Draft Project Impact Report - Boston Redevelopment Authority

Exeter Residences\888 Boylston
Observed Traffic Flow Disturbances
Existing Traffic Operations
\\Mabos\projects\09916.00\docs\Permits\DPIR\Text\DPIR Chapter 4
Transportation081208-clean.docx
As mentioned in the previous section, queue lengths on Exeter and Blagden Streets
were caused not only by the red signal at Huntington Avenue, but by double parked
vehicles which also contributed to less than ideal traffic flow. During the April 2008
data collection, in addition to queue length observations, several traffic flow
disturbances (in this case double parked vehicles), were also recorded. VHB staff
logged the number of vehicles that were double parked (related to the Copley Square
and Marriott hotels valet, delivery or loading operations) on Exeter Street and
Blagden Street, for seven days. The observed data collection sheets are provided in
the Technical Appendices.
The logs show that in fact double parking on the street does hinder traffic flow, and
therefore increases queue length, since vehicles have to merge from one lane into the
other in order to pass double parked cars. The merging in turn slows the traffic and
causes a slight delay. Although this delay caused minor interruption to traffic
operations, the overall operations on Exeter Street and Blagden Street did not
significantly change the level of service. Detailed field logs are included in the
Technical Appendices.
Level-of-service (LOS) is the term used to denote the different operating conditions
that occur on a given roadway segment under various traffic volume loads. It is a
qualitative measure of the effect of a number of factors including roadway geometry,
speed, travel delay, freedom to maneuver and safety. Level-of-service provides an
index to the operational qualities of a roadway segment or an intersection. Level-ofservice
designations range from A to F, with LOS A representing the best operating
conditions and LOS F representing the worst operating conditions. The evaluation
criteria used to analyze area intersections and roadways are based on the 2000
Highway Capacity Manual (HCM) 1 and the latest version of the SYNCHRO traffic
software (version 6.0), LOS D or better are considered to be acceptable levels of
service.
Level-of-service designation is calculated differently for signalized and unsignalized
intersections and for roadway links. For signalized intersections, the analysis
considers the operation of each lane or lane group entering the intersection and the
level-of-service designation is for overall conditions at the intersection. For unsignalized
intersections; however, the analysis assumes that traffic on the mainline is
not affected by traffic on the side streets. The level-of-service is only determined for
left turns from the main street and all movements from the minor street. The overall
1 Transportation Research Board, Highway Capacity Manual, Special Report 209, Washington, D.C., 2000
Transportation 4-13