A. Formula. The impact fee component for roads shall be calculated
using the following
formula:
TIF = FxTxA
1. "TIF" means the traffic impact component of the total development impact fee.
2. "F" means the traffic impact fee rate per vehicle trip in dollar amounts, for each
service area. Such rate shall be established in the Traffic Impact Fee Program Technical Document,
incorporated herein by this reference, 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, and as outlined in the Traffic Impact Fee Program Technical Document.
3. "T" means the trips generated by a proposed development and calculated according
to the Traffic Impact Fee Program Technical Document. The calculation of T described in 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 director of public works 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 Transportation Manager shall be guided by the most recent edition of the
Trip Generation Manual, Institute of Transportation Engineers.
4. "A" means an adjustment for the portion of anticipated additional tax revenues resulting
from a development which is prorated to system improvements contained in the capital facilities plan.
Such adjustment for traffic impacts is determined to be 15%, so that "A" equals 85%.