Sunday, February 17, 2013

Signal Timing Manual, 2nd Edition

NCHRP documents are influential in the
transportation industry and guide practice. 
I am reviewing a draft of the 2nd Edition of the Signal Timing Manual. One of my roles working for the City has been to review work more as opposed to produce it and this is just another example of this. This is especially true with the rewrite of the Signal Timing Manual. I am Chair of the panel that is providing a reivew of the draft documents and will serve to insure that the National Cooperative Highway Research Program (NCHRP) is of sufficient quality to put the Transportation Research Board stamp on the document. I am aware of several NCHRP projects that were never completed, so it is an important role to make sure that there is consensus and that the document reflects practice that would improve the conditions of traffic signals. The current project is titled NCHRP 3-103.

Of course, the First Edition of the Signal Timing Manual is a sterling example of a document that is one that has helped engineers, especially those that are unfamiliar with the details, to decipher practice that they may not be aware of. one of the issues associated with the Manual that was new to the field was the connection of traffic signals to regional policies. Chapter 2, specifically Section 2.1 highlights the importance of this and seeks to guide the engineer toward meaningful observance of the community's goals as opposed to those that are determined based on their own personal bias. In linking the engineer to the community's stated priorities, I believe the engineer takes a more important role in the organization and is able to focus on the implementation as opposed to defending themselves or their work.

The National Cooperative Highway Research Program is very influential in transportation engineering practice. It is important that multimodal considerations be taken when developing the guidelines. An example of one of the comments I had is shown below. It is a section on traffic signal detector design. The authors identified bicycle signals as a possible solution earlier in the chapter which was good to influencing that portion of the practice, but what's even more common than a bicycle stencil in a signal is the provision of detection for people on bicycles. In my previous blog post about the signal at N Winning Way and N Williams, the addition of an advance detector in the bike lane has reduced the delay for people on bikes by providing a little additional time for people on this approach, so that it is less likely they are skipped by the other movements at the traffic signal.

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An example of my comments for the signal detection portion of Chapter 4. 

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