On Monday, Caltrans opened the new carpool lane on the northbound side of the 405 between the 10 and the 90 freeways. Yay!

This means that it is now possible to carpool continuously between Westwood & Orange County on the northbound portion of the 405.

(Again, an interruption from my regularly scheduled blog entry to encourage you to post your commute today on Zimride, UCLA’s ridematching system: www.zimride.com/ucla.)

I look forward to reporting on the potential reductions in travel time, particularly for our regular commuters traveling from points south of the 90.

There is a story on the opening of the southbound 405 carpool lane  in today’s Daily Bruin by Melissa Joffe.  She includes quotes from folks around the campus with differing opinions on the new HOV lanes. James Bennett ’12 thinks that the lanes will cut his commute time from Westchester if only he could find a carpool buddy, while William Summerhill, a professor from the history department, thinks that the project “may have been a waste”, since he hasn’t noticed a difference in traffic.

Hmmm. Professor Summerhill’s quote raises questions consider some of the ways to measure the success of a carpool lane.

For starters, perhaps the benefits of a carpool lane are actually most directly received by actual carpoolers.

Professor Summer Mike Manville, a post-doctoral scholar  in the Lewis Center for Regional Policy Studies (and the instructor for a course called the Politics of Traffic Congestion -yes, there is such a thing), thinks that we commuters need to put things in proper context: Commuters should not expect carpool lanes to make a real dent in traffic; the new lane mostly benefits carpoolers, Manville told the Bruin.

And then there are some nerdier ways to approach this topic. One such way is in measuring the rate of flow: how many cars are able to travel past one particular point over, say, the course of an hour? On a road with a lot of cars where no one is traveling faster than, say, 20 miles an hour, I would reason that the flow rate is pretty low. If this carpool lane expansion increases the rate of flow for our carpoolers, that is supposed to be good, right? (An economist’s answer: It depends!) And if the rate of flow rises throughout all of the lanes to a satisfactory level, then might that be even better? (Or palatable?)

Here’s another way: We could count the number of people who are able to travel past a particular point. Through carpooling, a lane can carry more people. Couple this with the fact that a lane might have more cars traveling past a particular point because the rate of flow has increased, then the completion of a carpool lane seems like a pretty darn good idea.

Of course, it is worth pointing out that Professor Summerhill also said he traveled outside of peak travel times – in this case, he leaves his house at 5AM and leaves UCLA at 7PM – so perhaps he hasn’t had the chance to see the difference between travel speeds in the HOV lanes versus the regular lanes as vividly.

Congestion Pricing

Interestingly, Melissa also mentions congestion pricing in the same article. That might seem kind of random, but here’s the nexus: Metro is presently figuring out the logistics of turning two sets of carpool lanes, the El Monte Transitway and the Harbor Transitway, into HOT lanes. HOT stands for High Occupancy Toll. This has been done with success (more or less, depending on whose article you are reading) on SR 91 between Orange and Riverside Counties and on I-15 in San Diego County. The idea is that if you’ve got some carpool lanes with capacity – meaning that more cars could be added to the road without lowering the rate of flow to an unacceptable level (in this case, 43 mph – that’s like the magic number), then you could sell that excess capacity to drive-alone commuters, and use pricing to manage the demand for this opportunity.

This idea works even better, in both theory and practice, if you have two sets of carpool lanes in each direction. One reason is because motorists can go around cars traveling more slowly than they’d like.

Congestion pricing would increase the price for traveling on a toll lane based on the amount of congestion on the freeway, said Michael Manville, a doctoral student in urban planning. The point is not to make money but to move as many vehicles as possible, Manville said.

“The only policy we’ve found that reliably reduces traffic congestion is a policy that places a direct price on driving during congested times,” he said.

I don’t think we are going to see congestion pricing anytime soon on the 405.

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Do keep us posted on your experiences traveling on the 405. What are you observing? What are your travel times like now? (Please don’t be all grumpy on congestion pricing. That’s no fun to read.)