More on Traffic Mitigation

More on Traffic Mitigation

At its meeting on Tuesday, the White Flint Steering Committee had a brief “executive summary” of successful traffic mitigation efforts near the “trip capture area” of the Metro station (focussing on the Nuclear Regulatory Commission’s 50% reduction in commuter automobile use). In 2003, the Planning Board conducted a preliminary study of vehicular trip reduction in the area; the study was not definitive, and only indicated that further refinement of the data was warranted.

Here is a small part of the Planning Board’s material, from the LCOR No Bethesda Town Center Plan on 10/15/03 [courtesy of the Planning Dept, MNCPPC]:

Trip Reduction Due to the Site’s Unique Land Use Mix, Size, and Location 

            The total number of trips generated was determined based on trip-generation formulas that assumed each land use was located on a separate site and not located near a Metrorail station. These assumptions are not representative of the subject development on this site with a unique mix of residential and non-residential land uses on a large scale located within walking distance to Metrorail stations. Therefore, some of the total weekday peak-hour trips could be reduced as follows:  

1.            Internal Trips between Different On-Site Land Uses: As a large mixed-use development, from 10% to 25% of the trips could be between the internal different land uses: 

Between Land Uses Weekday Peak-Hour
Residential and Office Uses 15%
Office and Retail Uses 10% 10%
Retail and Residential Uses 25% 25%
Residential Use and the Movies   0% 25%

The percent of internal trips was determined based on studies of multi-use developments by the Urban Land Institute and the Institute of Transportation Engineers and Wells and Associates’ travel surveys conducted at Reston Town Center and Villages of Shirlington. The percent of internal trips is also consistent with those used for retail uses in the approved Traville development in North Potomac. 

The net trip reduction could be approximately: 

During the weekday morning peak hour: 13% or 472 person trips

During the weekday evening peak hour: 19% or 1,281 person trips  

2.            Non-Vehicular Trips: The site located within a walkable 1,000 feet of a Metrorail station (with a bus transfer facility) in a pedestrian friendly environment. Given the convenience availability of alternative transportation modes, between 5% and 50% of vehicular trips could be made by not driving single-occupancy vehicles. To encourage transit use, other TDM measures should include market-rates to park single-occupancy vehicles and transit fare subsidies.

These percents of vehicular trip reduction are shown below and were based on WMATA’s “Development-Related Ridership Survey II” and M-NCPPC’s Montgomery County Trip Generation Rate Study, dated August 1989, for offices located near Metrorail stations. 

Land Uses Weekday Peak-Hour
Apartments 40%
General Office Use 50% 28%
General Retail Use 25% 25%
Movie Theater   0%  5%

The net trip reduction could be approximately: 

During the weekday morning peak hour: 44% or 1,526 person trips

During the weekday evening peak hour: 25% or 1,626 person trips  

The net trip reduction by both could be approximately: 

During the weekday morning peak hour: 57% or 1,998 person trips

During the weekday evening peak hour: 44% or 2,907 person trips  

Barnaby Zall 

Barnaby Zall


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