The Down Town North second Traffic test Comment on "performance Metric and method"

WeMatter.com > PaloAlto City > Traffic (Second test plan) > Comment by Palo Alto Transportation department on Performance Metric and Method to Determine Percentage Change in Cut-through Traffic. (draft 2, July 20, 2004)

Thanks for the analytical paper and note (Performance Metric and Method to Determine Percentage Change in Cut-through Traffic. draft 2, July 20, 2004) ) - as well as for all the time you have spent in thiking about the problem of cut-through traffic in Downtown North.. Since this is late on a Friday afternoon and I have just received this document, I will resist  just now what would otherwise be a strong temptation to pore over it . I will add a few comments now, provide more next week, and will also forward this to Heba for her review. -- Joe Kott July 23, 2003

1.) There are implicit causal assumptions in your work regarding the economy and traffic (cut-through and otherwise) volumes. While it may seem commonsensical to posit a 1.0 (or some other) positive correlation between the two, the relationship is certain to be to some extent indeterminate (e.g. fewer commuter trips traded for more non-work trips?). There are likely to have been papers written for the annual Transportation Research Board (TRB) meetings that have explored the relationship between cyclical economic conditions and traffic volumes. I would suggest a review of these before making assumptions about the relationship between the two. I have not followed this research myself, so would be interested in finding out what you discover. My own view is that the relationship between economic conditions and traffic volumes is much stronger in the context of a regional freeway link or regional bridge crossing and much weaker in the context of a local street network.

2.) Other (non-economic) exogenous (to the relationship between a given traffic calming project and traffic volumes) variables are likely to alos be non-trivial. These include land development and re-development in the vicinity and the sub-region (which may only shift employment and other trips, not increase the aggregate number of such trips in the vicinity and sub-region), street network and traffic control changes (street repair and reconstruction projects, traffic calming projects in other nearby neighborhoods, new through and turning lanes, signalization improvements, incidents and crashes, special events, etc.) in the vicinity and the sub-region. 

3.) There is still a big assumption to deal with regarding the composition of the traffic counted at cordons or any place else. How much of it is through traffic? There are at present only two ways to determine this (the rest is guesswork): 1.) a proper origin and desitnation study as was conducted in 1999 for the Downtown North traffic calming plan (we can design the procedures and method for such a study should you and your neighbors wish - as we have done recently for the College Terrace residents) and 2.) interdicting or otherwise sampling a representative cross-section of motorists to find out if they had live or had business in the the neighborhood. This is, needless to say, hard to do these days.

4.) WIth these three points above in mind, it seemsto me to be better to choose a simple metric and method, both on the grounds of what is known and unknown about traffic composition and exogenous effects and also in consideration of the need to keep methods transparent and comprehensible (if possible) to the public and decision-makers.

Home,   Issues,   Links,   About us,   Contact-us,   The-book,   Site-map, mailto: support,

July 24, 2004 0:11