Are HOV lanes being well utilised?

by Gilbert Keith

I am on the SW Transit bus right now, heading home for a while the bus was on the Westbound HOV lane of 394, cruising at 60 or whatever. The thing is: all other non HOV lane occupying vehicles were cruising at 60 mph (if not faster) as well. Pn the other hand, Eastbound 394 was backed up, all the way to St Louis Pk/Golden Valley. So, I immediately asked myself: wouldn’t the HOV lane have been better used for all the EB travelers? Would we WB, public-transit-using folks, have been inconvenienced with using the regular lanes?

There are two ways to answer this, I guess. On the one hand, you can simply ask: what proportion of EB cars would have been eligible to use the HOV lane? If the answe to that would have been 1 in 5, then it surely would have made sense. If the answer had been 1 in 20, it probably wouldn’t lhave made sense. In the latter case it would probably have been better to just open up the 2 lanes for all EB traffic.

However, the situation can be approached another way. When the public planners were designing the HOV lane system, they probably had some data on the distribution of traffic flow. In particular, this data must have told them about the distribution of traffic flow, i.e. the mean rate at different time of the day, the standar deviation, kurtosis, skewness, etc. From this data, (and, of course, comparing the relative flows in each direction) they probably inferred that it is optimal to open up the HOV lanes to WB traffic from, say, 4-7 PM (I don’t know if these are the actual times, but for the sake of argument, let’s assume they are.) All is well and good, right?

Wrong. There will always be some outliers. I am willing to bet that if there’s a game at Target field at 6 PM, EB 394 is gonna be more crowded. If any other major route leading into downtown is closed there are probably gonna be more cars on EB 394, etc. The traffic flow rates, as I suggested above, will follow a distribution. On average they will take the mean value, but they might not. I think that might have been the case today, with a lot more cars going EB than going WB.

The immediate question that arises is: is it possible to control the HOV lane direction so that traffic flows are optimized? I think so. We probably have a lot of sensors on that road that give us a good idea of how traffic is flowing an a particular instant. Why don’t we leverage this information when we decide the direction in which traffic flows. It will lead to fewer headaches for those poor people stuck on EB 394.

Of course, I may be wrong about all this… but I really don’t think such is the case.

–Gautam
PS: I have reached home at this point. Happy Diwali to all readers.

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