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UPDATED: Traffic isn't going anywhere

Computerized traffic models help planners grade roads

Posted: October 10, 2008 9:09 p.m.
Updated: December 12, 2008 5:00 a.m.
Traffic is one of the most complained-about issues in the Santa Clarita Valley. Traffic is one of the most complained-about issues in the Santa Clarita Valley.
Traffic is one of the most complained-about issues in the Santa Clarita Valley.

Fifth installment of "The Big Picture," The Signal's in-depth series on population growth and development in the Santa Clarita Valley. Part 5 looks at traffic, one of the most complained-about issues in the SCV and one of the most frequently raised issues when local residents grouse about ongoing growth. Click here for the previous stories.

As city and county planners work on One Valley, One Vision - a new long-term planning document for the next 20-30 years - they are calculating how to cram more cars into the valley as the population nearly doubles.

Planners hope to release the traffic section of their plan next week, said Santa Clarita Senior Planner Jason Smisko.

The section shows how a population of 445,000 will affect the Santa Clarita Valley's existing and future major roads and freeways.

Planners look at a computerized traffic model to determine how much traffic each housing development generates and grade each major road on an A-through-F scale based on traffic institute standards, said city Community Development Director Paul Brotzman.

The traffic model includes vehicle trips that start in the Santa Clarita Valley, trips that end in the Santa Clarita Valley and trips that pass through the Santa Clarita Valley, said Senior Traffic Engineer Ian Pari.

The model compares a road's estimated volume with its capacity, Pari said.

Roads with an "A" rating are at about 60 percent capacity at peak hours, and roads rated "F" are over capacity at peak hours - or "basically gridlock," he said.

"Our goal isn't for everything to be ‘A' or ‘B.' Ideally, ‘D' is probably our target, and even ‘E' is acceptable in some situations," Pari said.

"D" conditions exist when the driver stops at a red light and gets to go on the next green, Pari said. "E" conditions exist when the driver waits through an entire signal cycle before proceeding.

"F" entails being stuck at a signal through several cycles.

"One of the big policy issues is what do you build for?" said Brotzman. "Do you build for peak-hour trips and have 10 lanes sitting there that may be empty for 22 hours a day?"

"Or do you have eight lanes, less asphalt, less environmental impact and have an hour in the morning or an hour in the evening when you drive a little bit slower," he said.

Ultimately, it will be up to the Santa Clarita City Council and the Board of Supervisors to decide, Brotzman said.

"We would not have released the land use map if we didn't think the traffic model was something that had the potential to work," Brotzman said. "Is it acceptable to the policymakers? We don't know yet."


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