40.620.010    Traffic Impact Fee Formula

The impact fee component for roads shall be calculated using the following formula:

TIF = F x T x A

A.    “TIF” means the traffic impact component of the total development impact fee.

B.    “F” means the traffic impact fee rate per trip in dollar amounts, for each service area. Such rate shall be established in the Traffic Impact Fee Technical Program Document for each service area by estimating the cost of anticipated growth-related roadway projects divided by the projected number of growth-related trips within that service area. Between major program updates, the calculated per trip fee will be adjusted annually to account for inflation using the Engineering News Record Construction Cost Index for Seattle.

C.    “T” means the trips generated by a proposed development and calculated according to the Traffic Impact Fee Program Technical Document, incorporated herein by this reference. The calculation of “T” described by the Traffic Impact Fee Program Technical Document includes, for some retail commercial land uses, a “business enhancement factor (BEF)” adjustment, based on policy considerations. In the absence of a land use code precisely fitting the development proposal, the Public Works director or designee shall select the most similar code and may make appropriate adjustments to the trip equation applicable thereto. In selecting the appropriate land use code and in making adjustments thereto, the director shall be guided by the most recent edition of the Trip Generation Manual, Institute of Transportation Engineers.

D.    “A” means an adjustment for the portion of anticipated additional tax revenues resulting from a development which is proratable to system improvements contained in the capital facilities plan. Such adjustment for traffic impacts is determined to be fifteen percent (15%), so that “A” equals eighty-five percent (85%).