§ 2.3.4. Capacity Analysis and Traffic Impact Assessment

Levels of service for roadways and intersections must be calculated before and after the proposed development. The acceptable methodologies for calculating levels of service are:

•  Operational Analysis from the Transportation Research Board Special Report 209, Highway Capacity Manual, 2000 (or most current version).

•  PASSER III-90 from the Texas Transportation Institute.

•  The TEXAS model, version 3.0, from the University of Texas.

•  Other methodologies approved by the Director of the Transportation, Planning and Sustaniability Department or his designee.

For diamond interchanges, the use of either PASSER or the TEXAS model is mandatory.

CORSIM or the VISSIM model may be required for analyzing U-turns at unsignalized intersections.

In a multiphased development, levels of service must be evaluated before and after each new phase. Unless otherwise indicated by staff in defining the scope of study, Level of Service D shall be the minimum acceptable standard. In addition, the following characteristics shall be addressed when evaluating capacity and level of service:

A.

Physical Configuration - intersection and roadway geometry.

B.

Traffic Characteristics - peak hour factor.

C.

Traffic Control - signalized and unsignalized control.

D.

Environmental Condition - topography, sight distance and other safety hazards.

E.

Capacity - as determined in the most recent edition of the Highway Capacity Manual.

The applicant must indicate all assumptions used in the analysis, including cycle length, phasing, G/C ratios, etc. Default values must be used for percent of heavy vehicles, peak hour factor, arrival type, etc. (see Table 9-3 of the Highway Capacity Manual) unless the applicant can document other values through field data.

A capacity analysis must be performed for key intersections within and adjacent to the site, as well as major intersections determined in the scope of the TIA. Level of service and volume/capacity ratios must be provided for each movement within the intersection. For residential streets, the TIA must also address desirable operating levels as specified in Sections 25-6-113, 25-6-114, 25-6-116, 25-6-141, 25-6-142 and 25-6-143 of the Land Development Code.

The TIA must present conclusions regarding the impacts of the proposed development on the roadway system. These conclusions should be expressed in quantitative terms whenever possible. The report must specifically address any adverse traffic impacts (level of service E or worse) which cannot be avoided if the development occurs. Transit-related issues should also be discussed if applicable.