ATTACHMENT 4

DISCUSSION PAPER

Traffic Counts and Projections

Related to Proposed UNC Modification of Development Plan

Prepared by Chapel Hill Planning and Engineering Departments

June 13, 2003

During review of this application, several citizens have made inquiries about traffic counts, traffic projections, and procedures for traffic impact analysis.  We prepared the following paper as background information about these issues.

We have received an application from the University of North Carolina at Chapel Hill, requesting approval of a Modification of the Development Plan for the central campus. 

This application proposes to modify the Development Plan approved by the Town Council on October 3, 2001.  The focus of evaluation has been on the changes proposed, and on the differences in impacts of the development proposed, compared to the impacts of the development approved in 2001.

The application proposes several changes to the University Development Plan that involve transportation issues.  Those changes include the reconfiguration of parking spaces on campus, changes in access to proposed Family Housing along Mason Farm Road, and the proposal of utility corridors and a parking deck in the vicinity of a potential fixed guideway transit corridor.

The net total of new parking spaces that would result from approval of the proposed changes to the Development Plan is 29 (an increase from 1,550 to 1,579).  The main difference is in the location of approximately 900 of those spaces (reallocated from the deleted Manning Drive parking deck to two new, smaller decks). 

The traffic impacts of the proposed change would be mainly in two areas:  South Columbia Street and the vicinity of the Boundary Street-Battle Lane-Country Club Road intersection.  This paper discusses data and methods of projection used to evaluate the traffic impacts of these proposed changes, with a focus on South Columbia Street.

There are two sets of numbers that have been discussed and, on occasion, compared.  The first set is a Transportation Impact Analysis submitted by the University in accordance with the Traffic Analysis Guidelines adopted by the Council for use in evaluating University development plans in the OI-4 zoning district.  The second set comes from a State/Regional transportation planning initiative, with NC Department of Transportation traffic counts serving as input to a regional transportation model.

DATA SOURCES

Traffic counts are routinely gathered, by placing tubes across travel lanes of a roadway to count the number of vehicles traveling that segment of roadway in a given period of time.  Counts are typically gathered and reported as 24-hour counts. Data are reported as “Average Daily Traffic” (ADT) or “Average Daily Vehicles” (ADV).  The terms are synonymous. 

The North Carolina Department of Transportation has been counting vehicles on South Columbia Street every two years for the last decade.  The University retained a consulting firm to gather counts, as required by Town regulations, and performed counts on South Columbia Street in October 2001 (at approximately the same time as one of the sets of NCDOT counts).  The next set of counts is required by the Development Plan approval to be taken in October, 2003.

Counts are used to establish benchmarks, which are then used in the projection of future traffic volumes.

PROJECTION METHODOLOGIES

Counting methodologies are standard and straightforward.  By contrast, there are many methods and algorithms used to project future traffic volumes.  In part, the appropriate method to use for a particular purpose is governed by the nature of the questions being asked.  For example, the projection method appropriate to use in a Transportation Impact Analysis for a new office building in a particular location may be quite different from what would be needed to project long-term, regional transportation patterns.

In this case, the method used for the University’s Transportation Impact Analysis followed guidelines established by the Town Council for this purpose.  Counts were taken in October, 2001, and are to be updated biennially.  The data will be updated in the fall of 2003.  Projections are based on expected trip generation, based on changes in parking on campus (different from other projection techniques which are typically based on changes in square footage of buildings).  Parking sites are identified and the number of trips per day projected, in different directions and in multiple paths, based upon historic patterns and local information.  Volume (expressed in terms of Average Daily Vehicles) is projected for the year 2010, with one projection assuming a specific level of University development and a second set of projections assuming no University development.

The regional 2025 Transportation Plan uses a model constructed to project regional transportation movements, with focus on volumes at key corridors and intersections.  Assumptions are made about mode split (cars vs. bus vs. transit vs. walking vs. bicycling), travel behavior (combining trips), carpooling, time-of-day travel, and other key variables.  Volumes (expressed in terms of Annualized Average Daily Trips) are projected for the years 2005, 2015, and 2025.

COMPARISON OF UNIVERSITY AND 2025 PLAN NUMBERS

The following table compares counts and projections for South Columbia Street that are included in these two documents:  the Transportation Impact Analysis submitted by the University and the regional 2025 Transportation Plan.

Average Daily Trips on South Columbia Street

Year of Count ↓	Transportation Impact Analysis	Regional 2025 Transportation Plan
1997		17,500 (actual counts)
1999		16,000 (actual counts)
2001	18,470 (actual counts)	16,000 (actual counts)
Year of Projection ↓
2003	19,030
2005		17,500
2010 [Assume no UNC devt.] [Devt. as approved 2001] Devt. as proposed 2003]	[21,000] [25,100] [26,000]
2015		31,000
2025		20,000*
* Assumes high capacity transit in the South Columbia Street Corridor beginning in 2020, implementation of regional fixed guideway transit connections between Durham-Chapel Hill and Chapel Hill-Research Triangle Park, and a new southern entrance to UNC from Fordham Boulevard.

These projections, although produced using different methodologies for different purposes, yield similar results through 2015.  Estimating a 2010 number for the regional model by taking the midpoint between 2005 and 2015 would result in 24,250 Annualized Average Daily Trips, compared to the University projection of 26,000 Average Daily Vehicles.

Looking ahead to the next required Biennial Transportation Impact Analysis (to be submitted by the University in December, 2003), we expect the next analysis to reflect an adjusted trip distribution methodology.  Projected vehicle trips for the Development Plan and the first biennial analysis were distributed on roadway segments using a computer model that was developed by the University with a set of assumptions specific to the Development Plan.  In this model, the University traffic consultant distributed the total number of trips to only study area streets rather than the overall downtown network.  We brought this to the attention of University representatives and they agreed to develop a new trip distribution model based on the full street network.  The December 2003 biennial and subsequent TIA reports will be prepared using the new trip distribution model.  We believe that because the same number of vehicle trips will be distributed through more intersections and street segments, a number of intersections in the next analysis will show fewer trips and some intersections may have a few more trips.

SUMMARY

The proposed changes to the Development Plan would result in some changes in vehicular traffic patterns.  We believe that the data sources and projection methodologies used by the University in preparation of its Transportation Impact Analysis are reasonable and consistent with guidelines that the Council has adopted for evaluation of traffic impacts caused by University development.  The methodology used here is specifically designed for evaluation of these impacts.  We believe that the projections offered in the Transportation Impact Analysis are valid and reasonable.