Chapter 29.08
TRANSPORTATION IMPACT STUDIES

Sections:

29.08.010    Transportation impact study.

29.08.020    Procedure.

29.08.030    General meeting or pre-application conference.

29.08.040    Determination of base assumptions.

29.08.050    Pedestrian analysis.

29.08.060    Submittal.

29.08.070    Review agency comments and recommendations.

29.08.080    Transportation impact study report contents.

29.08.090    Project description.

29.08.100    Existing conditions.

29.08.110    Description of existing transportation system.

29.08.120    Capacity analysis and quality of service.

29.08.130    Future traffic projections.

29.08.140    Project traffic.

29.08.150    Total traffic projections.

29.08.160    Site design and circulation evaluation.

29.08.170    Transportation impact analysis.

29.08.180    Calculations for capacity and quality of service.

29.08.190    Mitigation measures.

29.08.200    Transportation demand management (TDM) measures.

29.08.210    Transit capacity and access improvements.

29.08.220    Traffic signal operational improvements.

29.08.230    Street widening and other physical improvements.

29.08.240    Neighborhood transportation impact analysis.

29.08.250    Conclusions.

29.08.260    Recommendations.

29.08.010 Transportation impact study.

The transportation impact study (TIS) will assess the impacts of proposed development on the existing and planned street system. Comprehensive and coordinated transportation planning is critical to providing a balanced transportation system. The application of sound design principles for new streets, preserving street capacities in existing areas, ensuring smooth traffic flow, accommodating all transportation modes, and preserving or increasing safety are part of the TIS. To evaluate the impacts of development proposals on the transportation system, a professionally prepared TIS shall be required. This chapter provides standards for the preparation of a TIS. In addition, the following documents shall be referenced for more detailed information:

(a)    Grand Junction Circulation Plan.

(b)    City standard details.

(c)    Transit Design Standard Guidelines (Chapter 29.52 GJMC).

(d)    Corridor guidelines.

The primary responsibility for assessing the transportation impacts associated with a proposed development rests with the developer, and but not limited to the City, County, CDOT or RTPO serving in a review capacity.

(Res. 39-04 (§ 2.0), 4-21-04)

29.08.020 Procedure.

The following required steps describe the procedures required for the preparation and submittal of a TIS:

(a)    General meeting or pre-application conference.

(b)    Determination of base assumptions.

(c)    Submittal.

(d)    Review agency comments and recommendations.

(Res. 39-04 (§ 2.1), 4-21-04)

29.08.030 General meeting or pre-application conference.

(a)    As a general rule, a TIS shall be required for all land use applications for new development in the City and as required by the Mesa County Land Development Code. The requirement to prepare a TIS – or portions of a TIS – may be waived by the Transportation Engineer if the peak hour trip generation of the proposed project is less than 100 trips. If the applicant can demonstrate to the satisfaction of the Transportation Engineer that no other concerns exist with the transportation aspects of the proposed project, then a memo shall be prepared by the transportation consultant documenting the trip generation of the project and conclusions of the TIS.

(b)    The 100 peak hour trip threshold is consistent with the Colorado Department of Transportation thresholds for requiring impact studies on State highways. The following are examples of developments that produce approximately 100 trips in the peak hour:

(1)    One hundred single-family homes.

(2)    Forty thousand square foot office building.

(3)    Fast food restaurant.

(4)    Twenty thousand square foot shopping center.

    These thresholds are found in the Institute of Transportation Engineers’ Trip Generation. The latest edition of Trip Generation is adopted and incorporated by this reference.

(c)    At the pre-application meeting the applicant shall provide information regarding:

(1)    The project including type of land use (single-family, townhomes, multifamily, office, retail, etc.) and size (number of dwelling units, square footage, etc.).

(2)    The project site plan showing all proposed access locations and proposed land uses in relation to the accesses.

(3)    Anticipated project completion date and project phasing.

(4)    Any other information necessary or required to evaluate the project.

(d)    The appropriate agencies shall review the project information and provide comment regarding transportation issues including, but not necessarily limited to, accesses (locations/type), impacts on adjacent neighborhoods, the size of the study area and the study methodology.

(Res. 39-04 (§ 2.1.1), 4-21-04)

29.08.040 Determination of base assumptions.

(a)    After the pre-application meeting, the Transportation Engineer will evaluate the TIS – Base Assumptions. The consultant preparing the TIS shall complete the base assumptions form. The assumptions once approved shall confirm the base parameters and assumptions to be utilized by the traffic consultant in preparation of the TIS.

(b)    A base assumptions form shall specify:

(1)    Study area boundaries;

(2)    Period of study;

(3)    Growth rates;

(4)    Study intersections;

(5)    Time periods for study;

(6)    Trip generation rates;

(7)    Trip adjustment factors;

(8)    Overall trip distribution;

(9)    Mode split assumptions;

(10)    Committed roadway improvements by other projects, CDOT, Grand Junction and Mesa County;

(11)    Other relevant transportation impact studies;

(12)    Areas requiring special study.

Transportation Impact Study

Base Assumptions

(Res. 39-04 (§ 2.1.2), 4-21-04)

29.08.050 Pedestrian analysis.

The Transportation Engineer shall complete the Pedestrian Analysis Worksheet. This form will be used to identify origin and destination pairs for analysis by the consultant of pedestrian quality of service measurements for directness, continuity, street crossings, visual interest/amenity, and security. Based upon the project’s land use classification, consideration shall be given to the noted destinations that are located within one-quarter mile of the project site. Destinations farther than one-quarter mile may be specified, for example a school walking area boundary.

Pedestrian Analysis Worksheet

(Res. 39-04 (§ 2.1.3), 4-21-04)

29.08.060 Submittal.

Copies of the TIS shall be delivered to the appropriate City or County Community Development Department, to be submitted as part of the required planning information. Revisions to the TIS shall be made as required if the revisions are necessary to have a complete TIS or where changes to the site’s access necessitate additional revisions to the study. Electronic files of capacity analyses must be submitted with the TIS.

(Res. 39-04 (§ 2.1.4), 4-21-04)

29.08.070 Review agency comments and recommendations.

The review agency or designee shall analyze, evaluate and/or review TIS according to the adopted standards. Evaluative comments concerning the TIS shall be forwarded to the project planner. The project planner shall provide all review agency comments to the applicant. As a result of the engineering review the applicant may be required to perform and submit supplemental analyses of and/or address specific transportation issues or prepare, perform and submit a new study. Engineering review shall, to the extent practicable, cite by reference to this manual, the code, laws, rules or regulations deficiencies in the TIS.

Review and evaluation of TISs are and shall be initially and principally based on local conditions and community expectations as articulated by local government and its officials. An example of such a local expectation is that signal operations will not be optimized by eliminating existing left-turn phasing.

If the TIS is based on assumptions that conflict with local conditions and/or community expectations which may affect the usefulness or predictive proven by the TIS, the TIS will be rejected.

(Res. 39-04 (§ 2.1.5), 4-21-04)

29.08.080 Transportation impact study report contents.

A Colorado licensed professional engineer shall prepare the TIS. The engineer shall have experience in the area of traffic and transportation engineering. A statement of qualifications must be included in the submitted study. Certification as a Professional Traffic Operations Engineer by the Institute of Transportation Engineers is preferred. Each TIS shall address:

(a)    Project description;

(b)    Existing conditions;

(c)    Future background traffic projections;

(d)    Project traffic;

(e)    Total traffic projections;

(f)    Future total traffic projections;

(g)    Site circulation and design evaluation;

(h)    Transportation impact analysis;

(i)    Mitigation measures;

(j)    Neighborhood transportation impact analysis;

(k)    Conclusions;

(l)    Recommendations;

(m)    Any other information necessary or required to evaluate the project.

(Res. 39-04 (§ 2.2), 4-21-04)

29.08.090 Project description.

A description of the proposed project shall be prepared and include the type of land use and size of the proposed project, generally known as density and intensity. Intensity may be described in terms of floor area ratio or square footage of proposed development. Phasing plans shall be proposed, including the anticipated completion date. The proposed site plan shall be included; the site plan shall include all proposed vehicular access locations, dimensions and movements shall be described. The project description shall include a description of how pedestrian and bicycle travel shall be accommodated. This shall include a discussion of types of sidewalks (attached/detached), pathways, and connections to local and perimeter destinations.

(Res. 39-04 (§ 2.2.1), 4-21-04)

29.08.100 Existing conditions.

The TIS shall identify the existing transportation system conditions. Existing conditions shall include a description of the surrounding roadway network, bicycle facilities, and pedestrian facilities; an evaluation of the peak hour capacity and level quality of service at the study intersections and traffic accident history.

(Res. 39-04 (§ 2.2.2), 4-21-04)

29.08.110 Description of existing transportation system.

(a)    The study description of the existing roadway network shall include, but not necessarily be limited to, the number of travel lanes, presence or lack of pedestrian and bicycle facilities, posted speed limits, and adjacent land use(s). Traffic and intersection data compiled by the City and/or County Engineering Departments may be available. All recent (within two years) average daily traffic data that is available for the roadway network shall be shown on a figure in the study. Intersection peak hour traffic data shall be no older than one year; if new counts are necessary this is the sole responsibility of the applicant. The applicant may, at the direction of the Transportation Engineer, be required to collect data at a shorter interval. All traffic count data shall be included in an appendix to the TIS.

(b)    The TIS shall describe the existing bicycle and pedestrian facilities and shall include any facilities directly adjacent to the project site and within one-quarter mile or as described in GJMC 29.08.050, Pedestrian analysis. The Grand Junction Circulation Plan shall be referenced and complied with for planned pedestrian and bicycle facilities within the study area boundaries.

(c)    Bicycle facilities are defined by AASHTO Guide for Bicycle Facilities as:

(1)    Bicycle route means a street which is officially designated and marked (by signage) as a bicycle route, but which is open to motor vehicle travel and upon which no bicycle lane is designated.

(2)    Bike lane means a portion of street which has been designated (by paint stripe, pavement markings, and signage) for use by bicyclists.

(3)    Bike path means a separate trail or path from which motor vehicles are prohibited and which is for the exclusive use of bicycles or the shared use of bicycles and pedestrians.

(d)    Special attention shall be given to the bicycle and pedestrian connections to specific uses including but not limited to: schools, parks, employment centers, commercial areas, shopping, and adjacent land uses.

(Res. 39-04 (§ 2.2.3), 4-21-04)

29.08.120 Capacity analysis and quality of service.

(a)    The procedures set forth in the latest edition of the Highway Capacity Manual (HCM) shall be used in analyzing the capacity and operational characteristics of: vehicular (at the study intersections), pedestrian facilities, and bicycle facilities.

(b)    HCM delay and queuing worksheets shall be included in the appendices to the TIS report.

(c)    Roundabout analyses shall use SIDRA software or approved methodology. All worksheets shall be included in the appendices of the TIS report.

(Res. 39-04 (§ 2.2.4), 4-21-04)

29.08.130 Future traffic projections.

(a)    The future traffic projections shall be determined for each of the study years identified earlier as part of the base assumptions. Future traffic projections for the TIS analysis shall include:

(1)    Planned system improvements – capital projects;

(2)    Planned or in process development projects;

(3)    Background traffic growth.

(b)    A description of project-specific planned transportation system improvements identified in City, County or CDOT capital improvement plans shall be provided. This shall include, but not be limited to: signalization, intersection improvements, roadway widening, bicycle/pedestrian projects, and transit capital and operating/service improvements.

(c)    The future traffic analysis shall include known development projects that are within the study area and would impact the study intersections. Projects outside the study area currently being developed shall also be considered. Every project(s) and the cumulative effect shall be listed in the TIS and include location, size and proposed land use.

(d)    The background traffic growth within the study area shall also be accounted for when determining future traffic projections. Growth factors suggested by the consultant in the base assumptions form will be reviewed by the appropriate agency prior to use in the TIS.

(e)    The resulting future peak hour traffic projections at the study intersections shall be depicted on a figure in the TIS.

(Res. 39-04 (§ 2.2.5), 4-21-04)

29.08.140 Project traffic.

(a)    The transportation impacts of the project shall be generally determined based upon the following three-step process:

(1)    Determination of trip generation;

(2)    Determination of trip distribution;

(3)    Assignment of project traffic.

(b)    Trip Generation.

(1)    The trips generated by the project shall be determined and provided in tabular form. The trip generation shall be determined for total build-out conditions and for any development phases. The trip generation table shall indicate the number of average daily trips and peak hour trips.

(2)    The development of trip generation estimates for the project shall be based upon data from the latest edition of the Institute of Transportation Engineers Trip Generation. However, other data sources or trip generation rate studies may be utilized if the manual does not contain data for the type of project or other reliable data exists which better reflects the trip generation characteristics of the project. The use of other trip generation sources shall be discussed with the Transportation Engineer before being used, and if agreed, shall be memorialized in writing signed by the Transportation Engineer.

(3)    Adjustments to the standard trip generation of the proposed project may be made to account for internal site trips, pass-by trips, or other site-specific/project-specific characteristics of the proposed project. Adjustments for these characteristics shall be discussed with the City or County Transportation Engineer before use; in most cases the TIS shall follow guidelines set forth in documents such as the ITE Trip Generation. The adjusted trip generation for the proposed project shall be provided in tabular form or illustrated on figures.

Allowable Pass-by Factors

LAND USE

PASS-BY COMPONENT

Bank/S & L

15.0%

Regional Shopping Center

20.0%

Grocery Store/Community Shopping

30.0%

Hardware Store

10.0%

Strip Commercial

20.0%

Neighborhood/Convenience Center

60.0%

Fast Food Restaurant

45.0%

Gas Station

55.0%

(c)    Trip Distribution. The trip distribution for the proposed project shall be identified in the TIS. The distribution pattern shall be based upon: the project’s location within the urban area, the traffic model maintained by the MPO, existing traffic volume data, project marketing data, and engineering judgment. A figure showing the percentage of site traffic on each street shall be provided as part of the traffic study graphic material.

(d)    Trip Assignment. The project traffic shall be assigned to the roadway system according to the established trip distribution. The resulting project site generated traffic shall be depicted on figures for build-out conditions and any project phases. Daily and peak hour traffic volume information shall specifically be included.

(Res. 39-04 (§ 2.2.5), 4-21-04)

29.08.150 Total traffic projections.

The total traffic projections shall be determined for each of the study years identified in the base assumptions. The project-related traffic shall be added to the existing peak hour traffic. The resulting total traffic projections shall be depicted on a figure in the TIS. For each of the study years, the total traffic projections shall include the future traffic plus the project-generated traffic. The future total traffic projections shall be depicted on figures for each study year.

(Res. 39-04 (§ 2.2.6), 4-21-04)

29.08.160 Site design and circulation evaluation.

The project shall be analyzed to determine if the proposed circulation serves pedestrians, bicyclists and vehicles. The site design shall be evaluated to determine if facilities for vehicles, pedestrians and bicycles meet design standards and/or codes. The project shall comply with the adopted Grand Junction Circulation Plan.

The project shall be evaluated to determine if traffic flows are properly designed. Proper design shall minimize areas where motorists would tend to speed, minimize potential conflict areas between vehicles and pedestrians/bicyclists, and to establish circulation patterns that avoid unnecessary traffic congestion, cut-through traffic and conflict points. Adequate throat lengths for on-site stacking at exit points is required. At signalized driveways, the HCM ninetieth percentile worst lane queue model shall determine the necessary storage.

(Res. 39-04 (§ 2.2.7), 4-21-04)

29.08.170 Transportation impact analysis.

(a)    The TIS shall determine if the project creates any significant impacts at the study intersections and/or corridors within the study area boundaries. The peak hour capacity and quality of service at each of the study intersections and/or corridors shall be evaluated for:

(1)    Future background traffic conditions for each study year; and

(2)    Total existing traffic conditions; and

(3)    Future total traffic conditions for each study year.

(b)    The capacity and quality of service analysis for each traffic scenario and each study year needs to include mode split assumptions, if any. The findings shall be shown in the TIS in tabular form or illustrated on figures.

(Res. 39-04 (§ 2.2.8), 4-21-04)

29.08.180 Calculations for capacity and quality of service.

(a)    HCM delays and queues shall be calculated for signalized intersections using the latest version of the Highway Capacity Manual. The City of Grand Junction uses the TEAPAC signal analysis software and requires its usage and methodologies for design and analysis of signal timing. The HCM delay and queues shall be calculated for the identified peak hours for existing conditions, the projected traffic with build-out of the project, or at completion of phases of larger projects. An appropriate 15-minute peak hour factor shall be used. The performance evaluation of signalized intersections shall include the following:

(1)    Critical movements shall be identified and must meet or exceed the threshold requirement of 35 seconds of delay or less;

(2)    No movements shall have an adverse effect on the coordinated progression of the street system as determined by an approved coordination model consistent with the methods of HCM;

(3)    HCM ninetieth percentile worst lane queues shall be calculated and shall not obstruct upstream intersections or major driveways;

(4)    The analysis of a signalized corridor must show a reasonable progression band, identified as a usable (unblocked) band for major traffic movements.

(b)    Unsignalized intersections shall be analyzed using the latest Highway Capacity Manual methods. In the performance evaluation of stop controlled intersections, measures of effectiveness to consider include the delay, volume/capacity ratios for individual movements, average queue lengths and ninety-fifth percentile queue lengths to make appropriate traffic control recommendations. The Highway Capacity Manual recognizes that the delay equation used in the capacity analysis procedure will predict quality of service “F” for many urban intersections that allow minor-street left-turn movements, regardless of the volume of minor-street left-turning traffic. In recognition of this, the TIS should evaluate the results of the intersection capacity analysis in terms of all of the measures of effectiveness.

(c)    Roundabouts shall be analyzed using the latest version of SIDRA or approved methodology.

(d)    Street segment capacities shall be calculated using the following tables. The highest directional peak hour volume shall be used to calculate the segment quality of service.

 

Area Type

Functional Classification

CBD

CBD Fringe

Residential

Rural

 

Vehicles per Lane per Hour

Principal Arterial

600

700

850

1,000

Minor Arterial

550

650

750

850

Three-Lane Collector

500

600

700

800

Two-Lane Collector

450

550

650

600

Quality of Service

Volume to Capacity Ratio

A/B

0.00 – 0.90

C

0.91 – 1.00

D

1.01 – 1.10

E

1.11 – 1.20

F

Over 1.20

(Res. 39-04 (§ 2.2.8.1), 4-21-04)

29.08.190 Mitigation measures.

The TIS shall include feasible measures that would mitigate the project’s vehicular traffic impacts. The mitigation measures shall be in addition to the required improvements necessary to preserve corridor and intersection capacity. The acceptable mitigation measure(s) shall minimize the demand for trips by single occupant vehicles and increase the use of alternative modes. Mitigation listed in order of priority includes:

(a)    Transportation demand management measures;

(b)    Transit capacity and access improvements;

(c)    Traffic signal operation improvements;

(d)    Street widening and other physical improvements.

(Res. 39-04 (§ 2.2.9), 4-21-04)

29.08.200 Transportation demand management (TDM) measures.

(a)    Transportation demand management measures are designed to facilitate the use of alternate transportation modes in order to decrease demand on the roadway system by single occupant vehicles. Examples of TDM measures include:

(1)    Vehicle trip reduction incentives and services offered by employers to encourage employees to utilize alternative modes of travel such as carpooling, vanpooling, riding public transit, bicycling, walking and telecommuting.

(2)    Provision of a mix of land uses in close proximity, facilitating walking, bicycling or transit trips.

(b)    A detailed description of the proposed TDM measures and implementation plan shall be included in the TIS for any project seeking TDM-related trip reductions. If the proposed TDM program is acceptable to the Transportation Engineer, the applicant shall be allowed to reduce total project vehicle trips by an amount commensurate with applicable trip reduction policies.

(c)    The intersection capacity and quality of service shall be calculated to reflect the application of the proposed mitigation measures; the calculation shall show that the project-related impacts have been reduced to an acceptable delay for all movements and transportation modes (vehicle, bicycles, pedestrians). The findings shall be shown in tabular form.

(Res. 39-04 (§ 2.2.9.1), 4-21-04)

29.08.210 Transit capacity and access improvements.

Projects seeking transit credit shall document the proposed transit capacity credit and related reduction in total project vehicle trips. Examples of transit credits may include:

(a)    Contributions of equipment or funds to increase the capacity of existing transit systems;

(b)    Transit shuttles provided by applicant (e.g., bus, taxicab, van);

(c)    Contributions toward transit stations or centers.

(Res. 39-04 (§ 2.2.9.2), 4-21-04)

29.08.220 Traffic signal operational improvements.

Required traffic signal operational improvements may include upgrading signals with additional signal phases and/or signalization of an unsignalized intersection, addition of turn lanes and/or construction of a roundabout.

The need for new traffic signals shall be based on warrants established in the Manual on Uniform Traffic Control Devices, MUTCD. In determining the location of a new signal, traffic progression is of paramount importance. On arterial streets a spacing of one-half mile for all signalized intersections is necessary to achieve reasonable operating speed, capacity and optimum signal progression. Pedestrian movements shall be considered in the evaluation and adequate pedestrian clearance provided in the signal cycle split assumptions.

The applicant shall submit an analysis addressing proposed access, proposed signals and capacity and quality of service based on the City’s operational practices. All assumptions shall be documented in the TIS. An approved traffic engineering analysis must be made to properly locate all proposed accesses that may require signalization. The roadway to be analyzed for signal progression shall be established by the City or County and shall include all existing and proposed signalized intersections.

(a)    The progression pattern calculations must use a cycle length at least as long as current signal timing on the corridor under analysis.

(b)    Cycle split assumptions must relate to traffic volumes in the capacity analysis of individual intersections.

(c)    Approved computerized progression analysis techniques must be of the type which utilize turning movement volume data and pedestrian clearance times in the development of timing plans.

(d)    The green time allocated to the cross street shall be considered no less than the time which is required for a pedestrian to clear the main street using MUTCD standards.

(e)    Existing timing and phasing data for City and/or County signals on the corridor(s) being analyzed will be provided to the consultant on written request.

(f)    Elimination of or substantial changes to existing phases and/or changing cycle splits will not be allowed without written approval of the Transportation Engineer.

(g)    Existing signal operations shall be presumed to reflect the local conditions and community expectations as determined and directed by the Transportation Engineer.

(h)    If optimum usable bandwidth, as that term is defined by the Transportation Engineer, would be reduced if a traffic signal were installed then the intersection shall remain unsignalized and turning movements shall be limited.

(Res. 39-04 (§ 2.2.9.3), 4-21-04)

29.08.230 Street widening and other physical improvements.

Mitigation measures that include street widening and other physical improvements must be physically feasible and must meet minimum standards and code(s) for both on-site and off-site improvements.

(Res. 39-04 (§ 2.2.9.4), 4-21-04)

29.08.240 Neighborhood transportation impact analysis.

(a)    The TIS shall analyze the project impacts on adjacent residential areas. The need for this study shall be identified as part of the base assumptions. If it is determined that a neighborhood TIS is required the following procedure shall be followed:

    The applicant shall examine existing transportation conditions within the defined neighborhood. This shall follow the same procedure as set forth for the TIS. Daily and peak hour traffic volumes shall be collected for the local streets to be included in the analysis. Furthermore, the applicant shall:

(1)    Determine project-generated traffic for all modes within the neighborhood and show on a figure in the TIS.

(2)    Determine total traffic projections for the streets in the study area.

(3)    Determine if the impacts created by the proposed project are significant to the residential streets.

(4)    Develop measures, including but not limited to traffic calming techniques to mitigate impacts.

(b)    The neighborhood TIS shall also discuss how pedestrians and bicyclists would access the proposed project to/from the adjacent neighborhood(s), and the need for special facilities to enhance pedestrian and bicycle connectivity.

(Res. 39-04 (§ 2.2.10), 4-21-04)

29.08.250 Conclusions.

The findings of the TIS shall be provided in a summary report.

(Res. 39-04 (§ 2.2.11), 4-21-04)

29.08.260 Recommendations.

Recommended improvements/mitigation measures to achieve standards and safety improvements shall be stated. The recommendation section of the report shall describe the location, nature, and extent of proposed improvements. A sketch of each improvement shall be provided showing the length, width, and other pertinent geometric features of the proposed improvement.

(Res. 39-04 (§ 2.2.12), 4-21-04)