APPENDIX C
DESIGN GUIDELINES OF THE MERCER ISLAND DESIGN COMMISSION ADOPTED MAY 14, 1973

SIGN GUIDELINES

(Repealed by Ord. 04C-08)

ARTERIAL RIGHT-OF-WAY GUIDELINES

CONCEPTS:

The intent of the guidelines is to develop further goals and objectives synthesized from previous Mercer Island planning studies, the community and the Design Commission in order to provide a framework within which right-of-way improvements may be implemented that will result in a coherent, continuous right-of-way system representative of the island environment and complementary to its natural character.

The following GOALS, INTENTIONS and CRITERIA constitute a basis for evaluating improvements and development as they may contribute to the overall intended right-of-way system.

CLASSIFICATION:

In consideration of the general environmental characteristics of the Island, the arterial right-of-ways have been grouped into three general classifications which are applicable to Mercer Island: rural, suburban and urban. Several of the arterials may have more than a single classification depending on their basic character. For the purpose of developing guidelines, only the major distinct segments of an arterial have been differentiated.

Because there is general community consensus that the rural characteristics of the Island should be retained, right-of-way development must be evaluated, not only on the basis of the prevalent classification for any one arterial, but also on the basis of retaining and reinforcing the much-sought-after rural image. For this reason the suburban segments of any one right-of-way should be subordinated to the rural segments and development “downgraded” accordingly.

These arterials have also been assigned route and section numbers by the Public Works Department which are recognized by the Urban Arterial Board, as well as an arterial designation of major, secondary, and collector. However, since the guidelines deal chiefly with visual characteristics of the right-of-way, the arterial section designations have been introduced primarily as a means of reference. Diagrams keying the classification are found with the corresponding guidelines under rural, suburban, and urban right-of-way headings.

The rural right-of-ways are generally characterized by continuous vegetation belts, ravines, hillsides, winding roadways, group access drives, and relative freedom from infringing housing. These are the right-of-ways most highly characteristic of the Island environment and provide a unique exposure to Mercer Island for both visitors and residents. This category includes the majority of the Mercer Ways, Island Crest from SE 53rd Pl. to SE 68th, the majority of SE 53rd Pl., SE 68th east of Island Crest, and Gallagher Hill Rd.

The suburban right-of-ways pass through fairly dense residential communities d are characterized by closely adjoining housing, uniform front yard setbacks, individual driveways, and a lack of continuous vegetation buffers. This category includes SE 40th, SE 24th, 72nd SE, 78th SE, Island Crest from SE 40th to SE 53rd Pl., a portion of SE 53rd Pl., 84th SE, SE 68th and SE 72nd, SE 70th Pl., Merrimount Dr., and portions of the Mercer Ways.

The urban right-of-ways are the arterials within and adjoining the Business District. Island Crest north of SE 40th is the only right-of-way covered in this section.

TRAILS

A. BICYCLE FACILITIES

Different needs exist for bicycles in urban right-of-ways than in rural. The volume, composition and speed of vehicular traffic as well as topography generally dictate the type of system that should be provided. There are three basic types of bicycle facilities:

Shared Right-Of-Way (Class III Bikeway): a mixture of motorized vehicle and bicycle traffic in the same roadway; low vehicular volumes and speeds are a prerequisite.

Bicycle Lane (Class II Bikeway): a separately designated facility for bicycle traffic following the alignment of the roadway. The separation may be made by curbing, striping or buttons as required to insure bicycle safety.

Bicycle Path (Class I Bikeway): a facility that is separated from motorized vehicles and may or may not parallel the alignment of the roadway.

B. PEDESTRIAN FACILITIES

Pedestrian facilities exist for purposes of commuting, recreation, exercise, health and pleasure, and must accommodate a variety of uses. For example, a facility chiefly in use by children capable of quick, erratic movements needs special safety consideration. This is particularly applicable in areas where schools, parks, playgrounds, etc., are the predominant pedestrian traffic generators.

Likewise, surfacing materials must be compatible with the right-of-way, surrounding landscape, topography, and drainage conditions. Pathways may be paved, covered with gravel or wood chips, or simply left in their natural state (e.g. the pathway network along Island Crest Park owes much of its charm to its meandering, unpaved state).

There are two types of pedestrian facilities that may be implemented within the right-of-ways:

Sidewalk or Lane: adjacent to roadway, either paved (sidewalk) or unsurfaced (lane).

Path: independently aligned and generally landscaped to enhance the walkers’ experience.

C. JOINT BICYCLE/PEDESTRIAN FACILITIES

In areas where right-of-way widths, road conditions, or grades restrict separate bicycle/pedestrian routes, a joint facility may be implemented. It is particularly appropriate in situations where pedestrian traffic is minimal or grades are such to preclude excessive bicycle speeds. A joint facility, particularly one designed to accommodate two way bicycle traffic, may also be advantageous where excessive pavement widening may not be a desirable right-of-way improvement.

Joint Bicycle/Pedestrian Lane: following the alignment of the roadway, either directly adjacent or separated from the roadway.

Joint Bicycle/Pedestrian Path: independently aligned and separated from the roadway.

GENERAL GOALS

In order to enable a more specific consideration of the design criteria of individual right-of-ways, the general overriding considerations that are applicable to all right-of-ways are given here as reference for the more specific considerations that follow.

1. Develop right-of-ways consistent with the overall natural Island character and scale, with particular consideration given to any UAB and highway standards that may diminish the rural quality of the Island.

2. Emphasize key intersections and gateways that serve as an introduction to the Island by treating them in a manner that is representative of the best of the Island environment.

3. Develop views and vistas from the road as a means of locating and orienting the user to the Island.

4. Establish a safe and efficient system for all modes of acceptable traffic and encourage public transportation and pedestrian/bicycle facilities in appropriate locations, particularly in situations where they may serve schools and other public facilities.

5. Accommodate pedestrian/bicycle facilities by joint-use such as shared right-of-ways and joint bicycle/pedestrian facilities, with minimum widening of the paved surface.

6. Restore the Island environment and enhance the “street scene” by eventual undergrounding of utilities.

7. Provide direct and easy access to major Island “destination points”.

8. Link communities, neighborhoods and facilities.

9. Provide adequate information regarding speed, location, and public destination points.

10. Discourage on-street parking except as provided by emergency regulation.

GUIDELINES

RURAL RIGHT-OF-WAYS: majority of Mercer Ways, Island Crest from SE 53rd Pl., to SE 68th, most of SE 53rd Pl., SE 68th east of Island Crest, a portion of SE 70th Pl., and Gallagher Hill Rd. For route section locations see the adjoining map.

GOAL:

Retain, restore and enhance the natural Island environment as perceived from the right-of-way.

INTENT:

1. Treat the full length of the right-of-ways as a continuous road/Island experience.

2. Emphasize and enhance views to ravines and occasional views to the Lake, Seattle and the East Shore.

3. Retain the “rural road” atmosphere and minimize further disruption of the right-of-way within the “Critical Environment Zone” as previously identified, within which the majority of these right-of-ways lie.

4. Strengthen vistas and important axes.

5. Reinforce the image of the roadway as a continuum of the landscape elements adjoining the right-of-way.

6. Prevent further infringement of buildings, fencing and street furniture elements through the use of adequate vegetation buffers, building and street furniture setbacks as well as height and size restrictions.

7. Provide adequate lighting to delineate the roadway in keeping with its intrinsic appearance.

CRITERIA:

1a. Buildings should be sited to preserve the maximum natural vegetation buffer along the right-of-way.

1b. Use of predominant Island plant materials is suggested to buffer structures and reinforce the vegetation belts within the right-of-way, with special attention given to the reforesting of those areas that are in need of reinforcement or are an obvious break to the continuous vegetation enclosure of the right-of way. Private easements should be considered wherever buffers within the right-of-ways are not sufficient to provide the desired roadway enclosure. The easements should be planted and maintained by the City for a period of one year.

2a. Preserve existing views and vistas at locations designated as viewpoints by limiting building sites, restricting building heights, and encouraging selective clearing and/or planting of vegetation both within the right-of-way and outside it if possible. See arterial landscape master plan.

a. 3600 Block West Mercer Way

b. 3662 West Mercer Way

c. 82nd Ave. SE at West Mercer Way

d. 7600 Block West Mercer Way

e. 8200 Block East Mercer Way (midpoint of Avalon Dr.)

2b. Automobile turnouts should be developed at designated viewpoints to enhance the driving experience, provide for safe passing, accommodate school bus loading and emergency snow storm parking. Turnouts should be surfaced with pervious materials and, where location permits, should be left as much as possible in their natural state. Turnouts should be delineated by wood or log tire stops to prevent damage to groundcovers and low planting adjoining the roadway.

3a. Eliminate individual driveways in favor of group access drives in order to minimize disruption of roadways and vegetation.

3b. Limit the width of the road to two lanes, with additional pavement width permitted in curved sections where extra width may be required for safety purposes. Wherever possible, extend the plant materials to the pavement edge to further contain the width of the roadway.

4a. Strengthen vistas and important axes by selective clearing, elimination of conflicting street furniture elements such as utility poles, wiring, and fencing, and selection and planting of plant materials within the right-of-way that will heighten and emphasize the view.

5a. Repair all bank cuts and restore to near natural state cut and fill areas by replanting with indigenous plant material, with particular attention given to groundcovers that will help re-establish and retain slopes. Particular attention is directed to the planting and stabilization of banks along East Mercer Way. See arterial landscape master plan.

5b. On-street parking should be discouraged except at turnouts for designated viewpoints, trailheads, and during emergencies as stipulated by Resolution 504.

5c-6a. Buildings should be sited to preserve views of ravines and hillsides that are integral to the overall image and character of the right-of-way.

6b. Screen out all private fencing by planting buffers within the right-of-way if the fencing detracts from or is not in keeping with the overall roadway appearance.

6c. Screen all public utility installations visible from the right-of-way with adequate planting, and consider the use of ivy or similar vines along all chain link fencing except in specific instances where such planting may obstruct a view that contributes to the overall roadway experience and character.

7a. Lighting should be of a low level, more for the purposes of indicating the configuration of the roadway than for general illumination. The lighting standards should preferably be of wood and of a natural and unobtrusive finish, at a height of 12-16 feet. Lighting should occur at all intersections, at pathway/road crossings, and at private driveways wherever this is feasible without disrupting the overall spacing and sequence of the lighting. (Also see Public Signing, Lighting and Other Street Furniture.)

7b. Security lighting, gateway or driveway lighting should be used so as not to infringe upon the right-of-way where it may be a danger to the motorist and a hazard or nuisance to the pedestrian or bicyclist.

GOAL:

Encourage use of the right-of-way as a means of providing access to the Island’s ravine/open space system for recreational purposes.

INTENT:

1. Provide for bicycle and pedestrian use of the right-of-way.

2. Consider the open space trail system as an extension of the right-of-way and make it more readily accessible for public use.

CRITERIA:

1a. Maintain roadway to minimum widths as provided in 3b. above.

1b. Consider a number of bicycle turnouts along the Mercer Ways, removed from the vehicular traffic and developed in conjunction with a bicycle path system that could thus provide rest-stops for the round-Island cyclist.

1c. Insure safe pedestrian/bicycle crossings of the roadway at all intersections, and wherever topography dictates, allow for the relocation of the path from one side to the other, by signing and locating crossing within relatively straight road sections with maximum two-way visibility.

2a. Provide 1-2 car turnouts at all trailheads.

2b. Private easements should be evaluated in order to accommodate both bicyclists and pedestrians as an alternate to right-of-way use, particularly in locations where safety considerations demand segregation of traffic.

Easements should be secured on all new developments with connecting links through previously developed land obtained as opportunity arises. Easements should be obtained in keeping with the Island wide trail system.

1d-2b. Bicycle and Pedestrian Facilities:

a. Mercer Ways: Route 2 except for northern portion of section 2/10; route 5 except for northern portion of section 5/10; portions of section 6/20 and 6/40.

It is recommended that bicycle travel be accommodated along the Mercer Ways through a separation of the bicycle facility by a minimum setback of 5 feet from the roadway wherever topography permits. In considering the facility, extra care should be given to potential disruption of the right-of-way and its adjoining landscape. In some instances a continuous separately designated bicycle facility may be extremely difficult to implement.

Pedestrian lanes or pedestrian use of the separated bicycle facility should be considered, particularly along those portions of the Mercer Ways where school traffic or access to public open space trails must be accommodated.

b. Island Crest: Section 1/30.

A bicycle path could readily be implemented along the east side of Island Crest where a sufficient width of cleared right-of-way now exists to easily accommodate a two-way bicycle path. The setback from the roadway to the path should be planted with native trees and groundcovers similar to those that exist on the west side of the right-of-way.

The pedestrian path that now exists along Island Crest Park should be maintained because it is of a scale that is appropriate to the natural setting of the island. Special care should be taken in maintaining and reinforcing the existing trees and groundcovers within this portion of the right-of-way to insure that the character of the path, which is largely dependent upon its narrow and meandering nature, is maintained.

Pedestrian paths south of SE 63rd are recommended for the east side of the right-of-way adjoining the proposed bicycle path, with the Pioneer Park edge left undisturbed.

If portions of this section of Island Crest are widened to accommodate a turning lane to cross streets, extreme care should be taken to preserve the character of the right-of-way by retaining the existing vegetation edge along Island Crest and Pioneer Parks. The roadway pavement should be kept at a minimum width and medians resulting from the turning lanes should be planted with groundcovers and perhaps occasional trees that are in keeping with the existing native materials along the western edge of the right-of-way.

c. SE 53rd Place: Route 9 except for the western portion of section 9/20.

That portion of SE 53rd Pl. east of Island Crest, section 9/10 could easily accommodate downhill bicycle traffic by means of a shared right-of-way or a bicycle lane. To insure user safety due to the relatively steep grades, a separate bicycle facility to accommodate uphill traffic should be implemented. A unique opportunity exists for such a facility along the south side of the right-of-way which adjoins one of the major Island ravines and is uninterrupted by private driveways. The uphill bicycle facility could be implemented as a joint bicycle/pedestrian path, particularly appropriate for joint use due to the slow uphill bicycle speeds.

A bicycle facility along SE 53rd Pl. due west of Island Crest, section 9/20 should be implemented to facilitate cross Island travel when this arterial is completed. Every effort should be made to retain the rural character of the upper portion of section 9/20. This should be the major consideration and for this reason a shared right-of-way along this portion of the roadway is recommended.

A minimal pedestrian lane or path is recommended along this portion of SE 53rd Pl. as a means of accommodating pedestrian school traffic to the adjoining elementary school.

Informal clusters of native trees are recommended along this right-of-way, particularly along section 9/10 which should receive substantial tree planting in order to reduce the excessive width of the right-of-way and extend the adjoining ravine vegetation within closer proximity of the roadway. Clusters of trees should also be utilized to separate the roadway from the bicycle/pedestrian path. Groundcovers should be extended to the road and pathway edge.

With substantial planting, SE 53rd Pl. could visually become an integral part of the ravine, instead of merely skirting its edge.

d. SE 68th and SE 70th Place: The western two-thirds of section 0/10, route 10.

In order to keep the paved roadway to a minimum through this section of SE 68th adjoining Pioneer Park, a minimal bicycle path and a shared right-of-way should be adequate to serve both uphill and downhill traffic. The potential use of the easement along 92nd SE should be considered as a bicycle connection to East Mercer Way, by-passing the lower portion of SE 70th P1.

A combination of a pedestrian lane and path along one side of the roadway or a joint use of the bicycle path should be adequate to handle pedestrian traffic, since the network of trails within Pioneer Park can be expected to carry a substantial number of trail users along this section of SE 68th. The existing forest edge of Pioneer Park should be maintained. Groundcovers or grass should be extended to the road and pathway edge.

e. Gallagher Hill Rd.: Route 3 sections 3/30 and 3/40.

Due to the fairly high volume of vehicular traffic anticipated for Gallagher Hill Rd. as a collector/distributor to the I-90 interchange, special consideration is recommended for this right-of-way in order to maintain its present rural character.

It would appear that the extension of the bicycle facility along SE 40th would be better accommodated along Mercerwood Dr., for to safely implement a facility along Gallagher Hill Rd. would mean a substantial widening of the roadway pavement, particularly in view of its steep grades.

A pedestrian pathway could easily be implemented along the western side of the right-of-way, either along its full length or only the upper portions, as a means of providing pedestrian access to potential future public easements within the adjoining ravine.

GOAL:

Minimize disruption of the natural processes within the right-of-way.

INTENT:

1. Maintain and preserve natural drainage patterns that contribute to the ravine system and its vegetation.

2. Maintain and restore the visual continuity of the ravine physiography.

3. Control runoff, siltation and erosion.

CRITERIA:

1a. Within a period of one year, restore all scarred, retained and severely cut and/or filled areas that interfere with the natural drainage patterns.

1b. Daylight culverts with extra attention given to area to be drained, groundcover type, rainfall intensity, and slope.

1c-2. Plant native groundcovers on all cuts and slopes and secure with hemp matting as necessary to establish growth. Particular attention is directed to East Mercer Way. (See arterial landscape master plan.)

3a. Limit expansion and extent of paved surfaces by maintaining minimum road widths and using pervious surfacing materials for all turnouts and viewpoints or preferably leaving these unsurfaced wherever possible.

SUBURBAN RIGHT-OF-WAYS: (a) SE 40th, (b) SE 24th, (c) 72nd SE, (d) 78th SE, (e) Island Crest from SE 53rd Pl. to SE 40th, (f) SE 53rd Pl., (g) 84th SE, SE 68th and SE 72nd, (h) SE 70th Pl., (i) Merrimount Dr., (j) portions of Mercer Ways.

GOAL:

Enhance and develop the roadway as an extension of the adjoining properties within the context of the overall Island character.

INTENT:

1. Minimize disruption of adjoining residential community.

2. Provide for pedestrian and bicycle safety.

3. Delineate tile right-of-way corridor to enhance the roadway and adjoining community.

4. Reduce the apparent width of the roadway.

5. Maintain continuity with adjoining landforms and topography.

CRITERIA:

1a. Maintain minimum safe road widths. With the exception of Island Crest and portions of SE 40th and 24th SE, the two lane arterial should be maintained as the standard for all suburban right-of-ways.

1b. Wherever possible sufficient planting should separate the roadway from the adjoining residential community to maintain the continuity of the road and provide a degree of privacy to the adjoining housing.

1c-3a. Lighting should be of an intensity to provide general illumination to the right-of-way corridor in order to delineate the roadway, enhance its landscape treatment, and provide for user safety without disrupting the adjoining community or causing an excessive area-wide lighting effect.

Lighting standards should preferably be of wood or other materials with an unobtrusive finish. Standards should not exceed 22 feet in height. Additional lighting may be mounted at intersections, preferably by doubling the source on a single standard. (Also see Public Signing, Lighting and Other Street Furniture).

2a. Open drainage ditches should be converted to storm drains due to the need for bicycle and pedestrian provisions, particularly in light of the dense, single family communities adjoining the majority of these right-of-ways.

2b-3b. Obtain easements as necessary to allow for pedestrian, bicycle and vehicular separation as well as planting buffers.

3c. Private path or slope easements should be developed by the City, planted and maintained for a period of one year.

3d-4. Consider the use of street trees to delineate the roadway and reduce its apparent width, to shield the utility poles and wiring until eventual undergrounding, and to integrate the right-of-way with the adjoining community, with attention given to road visibility, particularly at intersections.

5. Repair all bank cuts and restore to near natural state, cut and fill areas by replanting with materials that will help establish and retain slopes, are in keeping with the adjoining residential community and the natural landscape character of the Island.

RIGHT-OF-WAY DEVELOPMENT:

a. SE 40th Street: Route 3, from West Mercer Way to Gallagher Hill Rd., including sections 3/10 and 3/20.

A combination of a bicycle lane and a joint bicycle/pedestrian path or lane with maximum separation from the roadway as permitted within the existing right-of-way should be adequate to accommodate two-way bicycle travel along SE 40th from 92nd SE to 70th or 76th SE, depending upon which route is used as an access to the Business District. Private easements should be considered as a means to provide more generous facility separation and planting buffers. The unimproved portion of SE 40th should be developed in a similar manner if and when the arterial connection is extended to West Mercer Way.

Wherever right-of-way conditions or easements permit the implementation of a pedestrian path, such a facility should be considered. Where a path is not feasible a lane or a joint bicycle/pedestrian path may be implemented, with special attention given to the separation of pedestrian and downhill bicycle traffic where high bicycle speeds may be a danger to the pedestrian.

There is an opportunity along SE 40th to introduce occasional street medians which should be planted as a further means of dividing the roadway. Occasional street trees in informal cluster patterns are suggested for this right-of-way both within the median and the planting buffers between the roadway, the pedestrian and bicycle facilities, and the adjoining property. Plant materials should be of a type common to the Island, but may be contrasted with occasional groupings of flowering or ornamental trees. Special recognition should be given to the plant materials of the adjoining properties and a pleasing transition achieved from the private to the public sector wherever this is appropriate.

b. SE 24th Street: Route 12 from West Mercer Way to 76th SE.

Due to steep grades and relatively high traffic volumes, bicycle facilities are not recommended for this arterial. Pedestrian sidewalks which are suggested for both sides of the arterial may accommodate uphill bicycle traffic. An alternate bicycle route bypassing SE 24th may be implemented along 72nd SE as a means of tying into North Mercer Way.

Street trees are recommended at approximately 30 feet on center along both sides of SE 24th. Plant material should be of the standard street tree variety, such as red maple, sycamore, oak, linden, etc.

The pavement width from 71st SE to West Mercer Way is excessive for a two lane arterial. It is recommended that the current width is maintained only to accommodate a left turn lane onto West Mercer Way with the remainder of the right-of-way devoted to planting and pedestrian facilities.

c. 72nd Ave. SE: Route 7, section 7/10.

Since closely adjoining residential properties make a separated bicycle facility along this arterial unrealistic, a shared right-of-way is recommended.

When the remaining open drainage ditches are covered, the pedestrian lanes that now adjoin the roadway are suggested for conversion to paths that are setback from the roadway by a planting buffer wherever feasible.

Informal cluster planting should be implemented within the right-of-way or easements secured for planting purposes, particularly along sections where the cover has been removed, in order to delineate the roadway and provide a measure of screening for the adjoining housing. Wherever possible cluster planting should be introduced between the roadway and the path to further enhance the walkers’ experience.

Special attention should be given to the use of informal cluster planting as a means of breaking up the extensive gravelled shoulders that extend from the right-of-way onto private property and are used for parking purposes by adjoining residents. Private easements should be obtained wherever additional planting would aid the streetscape, and planted by the City in conjunction with the overall right-of-way development.

d. 78th Ave. SE: Route 4, section 4/10 and that portion of section 4/20 south of SE 32nd.

Separate bicycle provision may not be necessary for 78th SE since 76th SE and SE 34th may easily be utilized as a designated shared right-of-way from SE 40th to the Business District. That portion of 78th SE from SE 34th to the Business District could be designated as a shared right-of-way or a bicycle facility could be implemented as part of the development of the Mercerdale site to provide access to the Business District from SE 34th.

If bicycle traffic is to be routed along 78th SE, it is recommended that a joint two-way bicycle/pedestrian path be implemented along the east side of the right-of-way. A separated sidewalk and bicycle lane could easily be implemented along the 80 foot portion of the right-of-way by limiting the adjoining local access drive to one-way traffic. This joint bicycle/pedestrian facility could also be implemented to accommodate a one-way bicycle route north, with use of 77th Pl. SE as a shared right-of-way to accommodate a bicycle route south.

Sidewalks along both sides of the arterial are the recommended pedestrian facilities.

That portion of SE 78th south of SE 40th could easily be utilized as a shared right-of-way to accommodate bicycle traffic from West Mercer Way to the Business District. Pedestrian lanes and planting are recommended as in c. above. An alternate facility may be a joint bicycle/pedestrian path along one side of the right-of-way.

SE 78th north of SE 40th is recommended for street trees and median trees at approximately 30 feet on center. Plant materials should be an extension of the sycamores, red maples and ivy used on SE 78th within the Business District.

e. Island Crest Way: Route 1, section 1/20.

Due to the high traffic volume and speeds along Island Crest, a bicycle lane or path, or a joint bicycle/pedestrian lane or path is recommended. In both cases, these facilities are recommended for consolidated two-way traffic in order to minimize the pavement expanse and provide optimum right-of-way landscaping.

Present use patterns suggest that a sidewalk along the west side in combination with a two-way joint bicycle/pedestrian lane or path along the east side of the right-of-way may be sufficient to accommodate the traffic along this portion of Island Crest. This joint bicycle/pedestrian facility may not be possible north of approximately SE 42nd unless additional easements are obtained due to the existing 60 foot right-of-way. By routing the bicycle traffic along 86th SE where a joint two-way bicycle lane can be quite easily accommodated, this northern portion of the Island Crest right-of-way could be generously landscaped. The joint two-way bicycle/pedestrian facility along the east side could be developed into an informal meandering lane to accommodate not only bicycle/pedestrian traffic, but also bus stops, seating and occasional turnouts for bicycle rest stops with generous planting buffers from the roadway.

Uninterrupted median street trees are recommended along Island Crest at approximately 30 feet on center from SE 40th to approximately SE 42nd of a type mentioned in b. above, providing left turn traffic can be accommodated.

Occasional medians to allow left turns to cross-streets are feasible from Merrimount Dr. south to SE 53rd Pl. Planting is recommended to be informal clusters of trees common to the Island and complementary to the natural forest edge on the west side of the arterial.

Informal cluster planting in the planting strips is recommended for both sides of the right-of-way, with occasional groupings of ornamental or flowering trees. Plant material should be located so as to best delineate the roadway, buffer adjoining housing, and reinforce the existing vegetation.

An alternate of street trees at approximately 30 feet on center should be considered from SE 40th to Merrimount Dr., in order to define the roadway along this stretch which is significantly devoid of trees, particularly along the east side. In this case, the informal cluster median planting would commence just south of Merrimount Dr.

Particular attention should be given to the selection of plant material along the west edge of the right-of-way, for it should reinforce the remaining natural forest edge, i.e., big leaf maple, Douglas fir, western red cedar, and bitter cherry.

Groundcovers should be native to the Island and relatively maintenance free, such as ivy, salal, and red fescue field grass. Wherever right-of-way groundcover areas adjoin private property, effort should be made to achieve a pleasing transition by the use of compatible materials or if appropriate, by the extension of the adjoining groundcover areas within the right-of-way.

f. SE 53rd Place: Route 9, western portion of section 9/20 only.

This western portion of SE 53rd Pl. should be developed in keeping with upper 53rd Pl. as a shared right-of-way or it may be developed to accommodate a bicycle path or lane. Pedestrian lanes or paths should be extended to West Mercer Way.

Particular care should be taken to insure that vegetation cover is restored along this right-of-way and all bank cuts properly replanted. It is recommended that informal cluster planting be utilized within the right-of-way as well as any easements obtained for planting purposes. Attention should be given to maximum screening of residential driveways in order to maintain continuity with the rural portions of 53rd Pl. to the east. Natural groundcovers in keeping with adjoining properties should be extended to the edge of the pavement and pedestrian pathway or lane.

g. SE 68th Street, 84th Ave. SE and SE 72nd Street: Route 10, sections 10/20 and 10/30.

A joint bicycle /pedestrian path or separated bicycle and pedestrian paths are recommended for the south side of SE 68th, adjoining the shopping center. The former could very easily be accommodated within the right-of-way without relocation of existing roadway, whereas an easement would be necessary to implement the latter under the same conditions. The separate pathway system is recommended for consideration since it would leave the natural edge of Pioneer Park undisturbed which may in time develop into a pedestrian pathway network similar to that now existing along Island Crest Park, and it would concentrate the pedestrian/bicycle activity adjacent to the shopping center.

A joint bicycle/pedestrian lane is recommended along the east side of 84th SE, to facilitate access to the shopping center and to serve the Junior High School. This may be extended as a path or lane along the south side of SE 72nd to West Mercer Way, or an alternate may be used of an uphill bicycle/pedestrian lane with shared use of the right-of-way for downhill bicycle traffic.

Street trees are recommended for the south side of SE 68th. Trees may be at approximately 30 feet on center and of the standard street tree types as mentioned in b. above, or may be informally planted in the planting strips separating the roadway and the bicycle and pedestrian facilities in keeping with Pioneer Park. Special care should be taken to maintain and reinforce the tree cover along Pioneer Park.

Median street trees and planter strip trees are suggested along both sides of 84th SE at approximately 30 feet on center from the eastern driveway of the school to SE 68th, with ivy or native grass suggested for use as groundcover. Street trees may be planted an the property line bordering the sidewalk along the west side of 84th SE without disrupting the existing sidewalk.

SE 72nd is suggested for informal cluster planting along the strip separating the roadway and the pedestrian or bicycle/pedestrian lane along the south side. Groundcovers should be in keeping with adjoining properties as in e. above.

h. SE 70th Place: Route 10, eastern portion of section 10/10.

Along SE 70th Pl. the bicycle/pedestrian facilities should be treated as an extension of upper SE 68th, that is a shared right-of-way or a minimal bicycle path along the south side, or the alternate use of the right-of-way along 92nd SE as a means of connecting to East Mercer Way.

Pedestrian paths or lanes are suggested for lower SE 70th Pl.

Special attention is directed to lower SE 70th Pl. where much of the tree cover has been recently lost. Informal cluster planting of native trees is suggested along this portion as a means of partially screening the adjoining housing and delineating the roadway. Native groundcovers should be extended to the edge of the roadway and adjoining pedestrian paths and lanes.

i. Merrimount Drive: Route 8

A shared right-of-way, or an alternate of a bicycle lane, to accommodate downhill traffic is recommended for Merrimount Dr. A combination of pedestrian paths or lanes could be implemented along one side of the right-of-way.

Use of native materials such as big leaf maple, western red cedar, bitter cherry, etc., is recommended along this right-of-way as a means of extending the natural forest edge which now dominates at the northwest intersection with Island Crest.

Planting of native groundcovers within the right-of-way is suggested as a means of further delineating the road and pathways. These should be planted to the roadway edge.

j. Portions of Mercer Ways: Route 2, northern half of section 2/10; portions of route 6, sections 6/20 and 6/40; route 5 segment of section 5/10.

Bicycle/pedestrian facilities should be developed in keeping with the adjoining rural portions of the right-of-way with particular attention given to the need for pedestrian and bicycle paths in areas where school traffic must be accommodated.

The segments of Mercer Ways classified as suburban are lacking tree cover enclosure and are very apparent disruptions to the continuity of the rural roadway experience. Planting is of particular necessity along these segments. It should reinforce the remaining forest edge where this is appropriate and in the more developed areas such as section 2/10, informal cluster planting of native materials is recommended as in c. above.

Of particular concern is the lack of landscaping in that portion of the East Mercer right-of-way directly adjoining the Mercerwood Shore Club, which is currently entirely paved and in need of a generous planting buffer in order to screen the pavement expanse of the Club’s tennis courts directly below the right-of-way.

URBAN RIGHT-OF-WAYS: Island Crest from SE 40th to I-90, route 1, section 1/10. All other urban arterials are covered in the Business Section.

GOAL:

Soften and breakdown the apparent scale of the roadway in order to make it more compatible with the natural Island environment.

INTENT:

1. Retain and reinforce the natural wooded hillside perimeter as part of the bowl-like enclosure for the Business District.

2. Treat Island Crest as the major gateway to the Island.

3. Facilitate pedestrian movement to the Business District from the surrounding apartment community.

CRITERIA:

1a. Consider the use of median and planter strip trees along Island Crest at approximately 30 feet on center from SE 40th to the I-90 interchange with particular care given to the appearance of the roadway from the adjoining apartment community as well as the preservation of the existing views to Lake Washington both from the roadway and the adjoining apartments.

2a. Consider screening the existing guardrail along the western edge of Island Crest by plant material hedging such as laurel, holly, yew, etc.

2b. Generous plant material buffers are recommended along the I-90/Island Crest interchange just north of SE 34th, as a means of buffering the adjoining Business District and apartment community and providing a greenbelt transition zone to the street through planting proposed above.

2c-3a. Maintain a narrow planter strip east of the existing sidewalk along the east side of Island Crest in order to provide a uniform planting buffer of ivy or similar vines along the rockery and retaining walls adjoining the sidewalk. Consider increasing the width of this sidewalk to 6 feet to facilitate pedestrian access to the Business District.

3b. Encourage a pedestrian crossing at SE 30th or SE 32nd as a means of providing pedestrian access to the Business District in keeping with the sidewalk-street tree concepts outlined in that section.

3c. Lighting should provide general illumination to the right-of-way corridor, be pleasing to the pedestrian, and of such intensity as to prevent area-wide lighting or disruption of the general view from the adjoining apartment community. Lighting standards should not exceed 24 feet in height and should be the same type of standard used in the Business District or compatible with it. (Also see Public Signing, Lighting and Other Street Furniture).

PUBLIC SIGNING, LIGHTING AND OTHER STREET FURNITURE

CONCEPTS

Public signing, street furniture and lighting elements should reinforce and clarify the predominantly natural, informal, residential character of the Island instead of dominating or detracting from it. Appropriate street furnishings can do much to make the Island environment more legible, expressive, pleasant and engaging as well as establish a “sense of place” about the Island as a whole or a particular area within it. Public signing can more effectively and uniformly reveal the function, form and activities of the Island and clarify its overall environment. “Out-of-control” signing, lighting and furnishings – ones that are in conflict with the surroundings – obscure the meaning of the environment as often as they clarify it.

Public signing, street furniture and lighting should be evaluated on the basis of 1) does it detract from the overall environment and 2) does it provide the type of information which clarifies and reinforces the environment of Mercer Island and provides the necessary guidance and orientation to the user.

GUIDELINES

Public Signing

Shape and color are the primary means of distinguishing the type of message for the driver in motion. The basic shapes are 1) the circle: mandatory rules; 2) the rectangle: guidance, speed regulations, and curb usage; and 3) the diamond: warning. Two nonconforming signs are the octagonal “stop” sign and the triangular “yield” sign.

Shape combined with color indicate a specific class of message. The red circle is used for prohibiting signs, i.e., no entry, no parking, etc. The green circle is used for permitted turning rules. The yellow diamond indicates warning. Blue rectangles give local guidance and green rectangles are used for distant guidance.

The use of symbolic signs as patterned after the international traffic symbols is gaining acceptance in this country. The 1971 Manual on Uniform Traffic Control Devices shows increased reliance on symbols with minimal word use as a transition toward a more uniform and better understood system of symbolic signing. There is no doubt that symbols, once accepted by the general public, offer greater clarity and legibility than the current, lengthy verbal directives in use. Because properly designed symbolic signing is more readily perceived and comprehended than its verbal counterpart, the number of necessary signs may be significantly reduced.

Mercer Island is, in a sense, a fairly remote community that does not receive a great deal of outside traffic, and for this reason has the need for relatively few public signs as compared to a community such as Burien or Renton which cater to a great number of outside visitors. This has a distinct advantage not only in keeping signs to a minimum, but also in introducing changes to an existing signing system.

Curb Usage Signs

Curb usage signs (no parking, bus stop, loading, etc.) although classified as Regulatory Signs, are not as important to traffic safety as other regulatory and warning signs, and thus offer a chance to introduce purely symbolic signing without compromising user safety.

The diagonally slashed red circle is an internationally accepted prohibitive symbol and is included in the Manual as acceptable signing for prohibiting truck and bicycle entry. The slashed circle, in conjunction with perhaps limited wording, may be used as the basis for most of the curb usage signing needed, within the Business District. (See diagrams.)

Warning Signs

Warning signs are primarily placed for the protection of the driver who may not be acquainted with the road conditions which may be potentially dangerous. Warning signs indicate crossings, curves, impending signals, slippery conditions etc. The majority of warning signs are diamond shaped with a black legend and yellow background. They are often used in conjunction with a rectangular verbal guidance sign.

Other Regulatory Signs

Other than the curb usage signs previously discussed, the major regulatory signs applicable to the Island are the stop, yield, speed limit, and turning signs. (See diagrams.) The signing for I-90 is not addressed by these guidelines.

Guide Signs

Guide signs are used to inform the motorist of interesting routes, destination, parks, trails, historic sites, etc. Because of the great familiarity of most users with the Island and its facilities, most standard guide signs are not needed on the Island and their use should be discouraged in order to maintain roadside signs to a minimum.

GUIDELINES

GOAL:

Encourage the development and use of an overall, uniform signing system in keeping with national safety standards and representative of the Island Community that will:

INTENT:

1. Emphasize symbols as opposed to the worded message.

2. Lend itself to combined or joint mounting so that the overall numbers of separate parts and separate signs may be reduced.

3. Lend itself to a uniform system of mounting.

4. Utilize light standards as supports for signing and light signalization where appropriate.

5. Be legible at the speed and distance at which it is placed to be seen.

6. Employ minimum sizes as determined by safety requirements.

CRITERIA:

Curb Usage Signs: Curb usage signs pertain mostly to the Business District. There are various other locations on the Island where “no parking” signs are used, but they are relatively few. Bus zone symbols may be used Island wide. Stopping or standing regulations may be particularly applicable at schools and other public facilities.

The spacing of “no parking” signs should not exceed 150 feet, and should in all cases be governed by what is a reasonable sight distance in each particular situation. “No parking” signs should be placed so that they are readily apparent from cross streets that enter in mid-block. Signs may occur at random spacing as determined by visibility and available mounting. Within the Business District, two signs per block may suffice.

Parking and other curb usage signs should be incorporated as part of the signing mounted on light standards within the Business District and in all other locations where possible in order to keep the number of upright posts at a minimum. The “no parking” sign/symbol may be the dominant element on all curb usage signs, with other uses such as truck load, bus zone, taxis only, etc., indicated by word message as part of the “no parking” sign. Symbols may be used to specifically indicate the permitted usage for a bus zone, taxi zone, etc., that are based on the open green circle which is the standard symbol signifying permitted use.

An alternative approach to posting “no parking” areas within the Business District would be to post only those limited areas where parking is allowed, providing a general “no on-street parking” sign/symbol is adequately displayed or incorporated as part of the gateway signing at key entry points to the Business District. In this case the positive green circle would be the basic symbol employed.

“No parking” designations within the Business District may also be incorporated by means of curb markings, striping, or by the use of the slashed red circle symbol as part of the curb shoulder. In this case the “no parking” designation should be used at approximately 40-50 foot intervals.

Reflector buttons for medians should be made a part of the curb. Use of upright reflector mounts should be discouraged.

Warning Signs: The use of warning signs should be kept to a minimum because their unnecessary use tends to lessen their impact. This is particularly true in the case of Mercer Island where the majority of motorists are very familiar with existing conditions. Low speeds, as well as a uniform, consistent, uncomplicated backdrop, such as that along the majority of the right-of-ways, present additional reasons for further reducing warning sign usage and sign size.

The color coding and diamond outline are of particular importance for easy identification of these signs, while the image in this case is of secondary importance.

Wherever safety considerations permit, the size of all signs and accompanying verbal guidance should be reduced in size as permitted by the Manual on Uniform Traffic Control. Use of symbols that offer greater legibility along with smaller size should be employed. Warning signs for trail crossings should be combined with actual trail signs wherever possible, particularly along the rural right-of-ways. The incorporation of the diamond warning symbol and verbal guidance message as a part of a rectangular background should be considered for it has distinct advantages for establishing a uniform mounting system and for the incorporation of additional signs.

Regulatory Signs: The majority of regulatory signs are rectangular with the long axis being vertical. Two notable exceptions are the octagonal “stop” sign and the triangular “yield” sign. Minimum size standards have been established for both “stop” and “yield” signs which are permitted on low volume local streets and secondary roads. These should be employed throughout the Island.

Where their use is necessary, turning signs should employ the green circle with arrow symbol as opposed to the purely verbal black and white signs. Turn prohibition signs should employ the red circle.

Speed limit signs should be kept at minimum permitted sizes, and where permissible they should be combined with other roadside signing.

Guide Signs: The only guide sign currently in use is the bicycle route sign marking an officially designated bicycle trail. The use of these signs will most likely increase as new bicycle trails and types of facilities are developed. New symbolic signing may be developed for bicycle route markers as well as designated viewpoints or trailheads. Signing should be kept at minimum sizes, used only where essential to differentiate the facility or identify its location, and mounted jointly with other signing wherever possible.

Mounting: All signing should be uniformly mounted. Signs should be mounted in conjunction with lighting standards and should be integrated with other signing wherever possible. Signs should be mounted in conformity with height and setback requirements. Upright posts should be of wood, stained in dark or neutral colors. The back sides of all one-face reading signs and metal mounting frames should be anodized or painted to closely match the color of the wood.

Street Name Signs: A distinct, well designed system of street name signing could do much to give Mercer Island special identity. The mounting and upright post should be compatible with that used for other public signing. The letter type should be picked for legibility and clarity. Value contrast as opposed to color should be emphasized to facilitate readability. Another alternative would be to incorporate the message “dead end” or an appropriate symbol as part of the street name sign with no change in color. A graphic symbol that is representative of the Island could be incorporated into all street name signs and used consistently to graphically convey “Mercer Island” in other locations, such as the gateway signing to the Business District.

An alternate to the use of the diamond “dead end” signs could be the color coding of street name signs for those streets that terminate as dead ends. For example, all through street name signs could be dark brown with white lettering; all “dead end” name signs could be signal yellow with black lettering.

Crosswalks: The major pedestrian crosswalks within the Business District should be indicated by a differentiation of pavement as opposed to striping. The pavement should be complementary to that used for adjoining sidewalks as well as pavement within the future town square which the majority of these crossings adjoin. It is the intent that paving within the town square as well as other pedestrian precincts, be of a unit type material such as concrete pavers, brick, tile, etc.

Lighting

GOAL:

Provide safety for vehicular traffic and pedestrians.

INTENT:

Provide the amount and quality of light as recommended by recognized standards while satisfying the other goals included here. Within the Business District an average of 1.2 f.c. may be used, which is the IES Handbook recommendation for “major” roadways in business districts not classified as downtowns. An average rating is not significant. The minimum level and contrast between minimum and maximum as perceived over time is more important, particularly along the rural right-of-ways. Incident light along commercial streets is a significant contributor to the amount of light perceived by the driver or pedestrian and should be considered as part of the overall light level.

CRITERIA:

a. Light Levels: The minimum light level provided by street lights within the Business District at a point furthest away from the light source should not be less than .2 f.c. and the maximum should not exceed about 5 f.c., the average level.of light should be approximately 1.2 f.c. to 2 f.c. including a maintenance factor of 60 percent.

b. Increase lighting levels at intersections, crosswalks and driveways to 2 times minimum, that of the remainder of the street or about 4 f.c. average at intersections within the Business District. Light should be uniform at intersections and of a contrasting color to mid-block areas.

GOAL:

Enhance the directional quality of the street.

INTENT:

1. Give character and scale to the street and emphasize the street corridor’s directional quality through lighting pattern, scale of the light standards, and increased light levels at points of increased decision making for the driver.

2. Reduce area wide lighting and restrict it to the corridor.

3. Focus on the enhancement of the landscape and reinforce one’s perception of the streetscape as a continuum of related elements building a total image.

CRITERIA:

1a. Emphasize the street as a corridor by focusing the lighting totally on the street and pedestrian ways. Minimize spilling-over light onto adjacent properties, except at driveways.

1b. At intersections and along major pedestrian routes in the Business District add pedestrian lighting integrated with the street lighting system. Light fixtures should be at a comfortable height to the pedestrian, approximately 10-15 feet high.

1c. Emphasize the lighting at intersections by changing the color of the light to warmer tones either by changing the type of lamp or the color of the lens.

2. Lighting standards should be not more than 20-24 feet high between intersections and 28-33 feet high at intersections in the Business District and along urban right-of-ways. Rural right-of-way standards should not exceed 16 feet; suburban right-of-ways should not exceed 22 feet. The lighting fixtures and standards are elements of a continuum of parts constituting the streetscape including trees, signs, roadway, automobile and people, which together form a spatial territory. Subjectively, not measurably, if the lights are raised above their critical heights they go beyond the bounds of the territory, break the tension formed between parts, and dis-associate themselves from the other elements. The road user at this point no longer perceives the lights as a cooperative part of the total streetscape.

3a. Placement of lights should complement street tree spacing.

3b. Light underneath portions of the trees with approximately 10 percent up-light of the street lighting system. (This portion may be increased as the trees mature).

GOAL:

Relate lighting to other public elements of the street.

INTENT:

Reduce the number of competing elements in the streetscape and through integrated design, relate, in terms of common or complementary materials, systems and scale, the lighting system to traffic signals, signing and street furniture.

CRITERIA:

a. Combine the traffic signals on the same standard or standard system as the general intersection lighting.

b. Integrate signing, street signing and directional signals with the lighting standards throughout the Business District, at major intersections and at other locations if appropriate.

c. All light standards should be of the same material, preferably wood.

d. Overhead traffic signalization should be kept at a minimum.

Street Furniture

GOAL:

Develop furnishings that are compatible and consistent with the surrounding “streetscape” and the overall Island environment.

INTENT:

1. Provide appropriate street furnishings where needed.

2. Encourage pedestrian use of the right-of-way.

3. Enhance the street scene.

CRITERIA:

The street furniture elements addressed by these guidelines are bus shelters, seating, guardrails, bollards, fire hydrants, signal control boxes, and trash receptacles.

Bus Shelters: Bus shelters should be installed at major collecting points where sufficient use justifies their location or at locations that are served by several transit routes. Joint use between public and school transit stops should be encouraged. Bus shelters should not occur on highly developed residential streets or restricted right-of-ways where they may infringe on adjoining private development. Shelters should be sited to give easy access and visibility of the right-of-way, protection from prevailing weather, rain, and sun. Seating should be incorporated as part of the shelter. For the Business District or at other major locations, appropriate trash receptacles should be provided.

The existing bus shelter in the 4800 Block of East Mercer Way is an excellent example of a rural shelter in terms of materials, scale, color, and orientation. It is of a sufficient size to provide adequate protection from the weather. It incorporates seating. Its roof form is pleasing and in keeping with residential housing, and it has a sense of overhead structure that implies “shelter”. The scale and color of the structure are good due to the use of natural unit materials. The above criteria should be applied to the development of future bus shelters or a prototype shelter for the Island.

Bus stop locations within the Business District should be located to take advantage of the existing shelter and seating provided by adjoining buildings, such as the National Bank of Commerce. This particular type of pedestrian oriented street frontage development should be encouraged throughout the District, in which case the bus shelters would not be a necessity. The location of separate shelters within the Business District, as it exists, may only reinforce the preponderance of very small structures and very large parking lots.

Seating: Seating may be incorporated into the proposed joint pedestrian/bicycle paths proposed along arterials such as Island Crest Way to serve transit and school bus patrons, or as resting stops for bicyclists, pedestrians, etc. Care should be taken to locate seating sufficiently set back from the roadway and in areas where it does not conflict with adjoining development. Materials should be of wood, either natural or stained in dark or neutral colors.

Guardrails: Guardrails that are used for street ends, undeveloped right-of-ways, and other similar locations where their use is more symbolic than safety-oriented should be of wood, either natural or stained in dark or neutral colors. Reflector buttons may be incorporated as part of the guardrail for night-time visibility.

In locations where wood guardrails do not suffice because of safety requirements, a planting hedge may be employed as a visual screening device. Where screening is not feasible corten may be employed as the rail. If existing speed limits are maintained on the Island, the use of such guardrails should be limited to Island Crest Way and I-90.

Bollards: Bollards may be used for marking street ends, roadways, and undeveloped right-of-ways particularly where unimpeded pedestrian traffic is desirable. Bollards may be used as a means of separating bicycle and vehicular traffic where curbing is not appropriate, and may be employed at intersections that are crossed by bicycle paths/lanes as a means of preventing vehicle entry. Bollards should be of wood, either natural or stained in dark or neutral colors.

Bollards used for the protection of fire hydrants should be left as natural concrete with the use of reflector buttons for night-time visibility. The use of bollards to protect stop signs or other signage posts should be kept to a minimum; where bollards are absolutely essential for safety purposes, they should be treated as above.

Fire Hydrant: Hydrants should be uniformly painted. Hydrants within the Business District should be undergrounded.

Signal Control Boxes: Control boxes should be located to allow screening by planting buffers.

Trash Receptacles: Trash receptacles should be incorporated as part of the overall streetscape elements. Their main use would be in the Business District, at bus stops and shelters, and other public facilities. Receptacles should be of a size that does not dominate the streetscape elements, and should conform to the State Litter Control Law. They should be attached to existing light standards or other appropriate elements, and should be free of the ground. Metal, perforated metal, or wire mesh may be used. Color may be chosen to blend with existing street elements or used as a contrast to them,

GENERAL GUIDELINES FOR PUBLIC, QUASI-PUBLIC,
AND MULTI-FAMILY DWELLINGS

(Repealed by Ord. 04C-08)