There is no “significant” traffic impact caused by the glut of new high-density housing planned and already approved in downtown Walnut Creek. And the City Council has the numbers to prove it. Of course, the way the Council has decided to quantify traffic impacts has a lot to do with this conclusion.
For most downtown intersections, traffic congestion is rated on a Level of Service (LOS) basis. The LOS ranks, on a scale of A to F, how long it takes traffic to get across an intersection. If you sail right through, or are only delayed for a short time waiting for the signal light to change, that’s LOS A. If the traffic light cycles are really long, and you’re sitting through multiple cycles before you can get through, that’s LOS F. LOS is analyzed for travel in all directions and all turns through an intersection. When traffic from a new project is projected to degrade service - especially by a letter grade – like from LOS D to E, or from LOS E to F, mitigation measures are required.
Level of Service used to be the City-wide standard, but a number of intersections downtown, especially along Ygnacio Valley Road were operating near critical levels. So, the City Council changed the rules.
The Council identified Ygnacio Valley Road as a “Route of Regional Significance” and declared that Level of Service no longer applies. It would be more appropriate, they said, to analyze traffic impacts on Ygnacio using the same criterion that applies to Highways 24 and 680.
Traffic impacts on freeways are measured by a “Delay Index”. The concept is pretty simple … you compare how long it takes to drive from POINT A to POINT B during commute hours with the time it takes when there is no traffic at all. If the commute drive time is more than double the non-commute drive time, you have a “significant” impact that needs to be addressed.
At first blush, this approach doesn’t sound unreasonable. But Ygnacio Valley Road isn’t a freeway. Freeways have no cross traffic or stop lights.
The Delay Index ONLY measures how long the east-west commute along Ygnacio takes – not how long it takes to CROSS Ygnacio if you happen to be traveling north-south on an intersecting street, or if you need to make a left turn.
Furthermore, there is really no such thing as an “uncongested” travel time on Ygnacio. Even if you’re not stuck in traffic, you will be stuck waiting through the notoriously long light cycles. If the delay is the same, whether caused by traffic lights or actual traffic, the Delay Index calculates out to an “excellent” 1.0.
The selection of “Point A” and “Point B” has a major effect on the calculation too. Unlike the LOS standard, which is measured at each individual intersection, the City has elected to ONLY calculate the Delay Index for the entire trip between Oak Grove Road and the Freeway. Even if a development, like the BART Transit Village, is likely to jam up one or two particular downtown intersections, the effect on the Delay Index calculation is diluted by factoring in the part of this lengthy route that isn’t affected.
I’m not the only one who thinks this methodology is flawed. The State Department of Transportation has also taken issue with the City’s approach to evaluating traffic impacts on Ygnacio. In comments to the Environmental Impact Reports of recently proposed projects, CALTRANS has stated that the Delay Index calculations are insufficient to gauge traffic impacts at the intersections with freeway on and off ramps.
So why would the City Council adopt Delay Index as the standard for analyzing traffic impacts? My answer is that the business and development interests, who help put the Council members in office, don’t want to allow environmental concerns to stand in the way of major (and very profitable) projects like the BART Transit Village or 1500 No. California Boulevard. I’d be happy to hear if anyone out there in the Ygnacio Valley can offer a less sinister explanation. Think about it when you’re stuck in traffic.
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