Improving Transportation Network Efficiency Through Implementation of Transit-Supportive Roadway Strategies (2016) / Chapter Skim
Currently Skimming:
Pages 129-141
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 129... ...
C-1 Appendix C Transit Signal Priority Impact Assessment INTRODUCTION The impacts of transit signal priority (TSP)
|
From page 130... ...
C-2 HCM 2010 formulae allow the delay impact to be estimated, given a particular change in green time due to TSP. According to the HCM 2010, the control delay d for a lane group at a signalized intersection is given by the following formula (HCM Equation 18-19)
|
From page 131... ...
C-3 I = upstream filtering adjustment factor, accounting for the effect of an upstream traffic signal on vehicle arrivals, from HCM Equation 18-3 (unitless) ; and cA = average lane group capacity (vehicles per hour)
|
From page 132... ...
C-4 Notes: v/c = volume-to-capacity ratio, g/C = green time to cycle length ratio, NP = no priority, e = green extension time in seconds. Figure C-1.
|
From page 133... ...
C-5 Table C-1. HCM Delay Adjustment Factors for v/c =0.60 Notes: v/c = volume-to-capacity ratio, g/C = green timeβtoβcycle length ratio, e = TSP interval length.
|
From page 134... ...
C-6 The adjustment factors shown above apply for estimating the delays on those signal cycles with transit priority. The average delay (seconds per vehicle)
|
From page 135... ...
C-7 ππππππ = ππππππ,π΅π΅π΅π΅ππP(bus)
|
From page 136... ...
C-8 SIGNAL PROGRESSION CONSIDERATIONS The decision to provide transit priority at isolated traffic signals considers primarily the availability of spare green time, that is, the time available in the cycle length after serving the traffic demands at the intersection approaches. Sufficient green time ensures that no oversaturation, and corresponding long delays, would occur for the non-priority traffic movements.
|
From page 137... ...
C-9 The arrival of a bus at the downstream intersection, given that priority is granted at the upstream intersection, depends on several factors, including the bus travel time, bus stop dwell time (if any) , intersection signal settings (e.g., offset, green times)
|
From page 138... ...
C-10 receives the spare time and starts early. This is shown as Ge in Figure C-6.
|
From page 139... ...
C-11 Simple criteria were developed to check whether the signal progression criterion is satisfied, on the basis of the type of priority provided, signal settings, and basic transit characteristics, as described below. Consider a pair of signalized intersections along an arterial as shown in Figure C-7.
|
From page 140... ...
C-12 The components of bus delay -- average dwell time, average re-entry delay (i.e., delay waiting for a gap in traffic when leaving the stop) , and acceleration/deceleration delay -- can be measured in the field or estimated using procedures given in the TCQSM (Kittelson & Associates, et al.
|
From page 141... ...
C-13 Finally, a key assumption for Equations (7)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.