Congestion pricing (also known as variable tariff and dynamic pricing) is a mechanism to charge different amounts for traffic at different times. As a simple example, you may have to pay 2$ for using a road at peak hours, and it may cost you only 1$ (or be free) at non-peak hours. Washington DC metro uses the same concept, although they have more than two tiers and have the dreaded peak of the peak charge as well. Airlines and hotels use the same concept, with their prices being computed similarly through a demand and supply mechanism. Generally speaking, congestion pricing is a good mechanism for passenger traffic, compared to appointment scheduling and network capacity management, which is usually used in freight traffic management systems, for example, NX FTMS.
However, congestion pricing (charging more) does not work, if you are not setup to charge anything at all! So a different mechanism is used at times – the one to only allow some vehicles on the roads. This is typically known as road space rationing. For example, you could choose to allow only blue cars on the road at one day, and the red cars on the road another day. Oh wait, you can’t actually do that as that appears to be politically motivated. So, let us try again. You can try to allow the cars that have the last digit of the license plate numbers odd on the road on one day, and the cars for which the last digit is even on another day. Then, you can turn those digits and days around as you wish to make sure that the system is fair and not gameable (and you may need to have some provision for vanity plates).
The best example of this that I have come up is in Bogota, where the system is called pico y placa, which combines the peak traffic hour (pico) also with the license plata (placa), although the peak hours have since 2009 been extended to almost the entire day (6 am to 8 pm). Knowing Bogota’s traffic, I think that is a fair characterization of the peak hour. The way the system works is that cars with number plates ending in 5, 6, 7 or 8 cannot driving between 6 AM and 8 PM on Mondays. Last digits for other days are:
- 9012: Tuesday
- 3456: Wednesday
- 7890: Thursday
- 1234: Friday
There are no restrictions on the weekends.
So, firstly we observe that if you have two cars, one ending in 5 and the other ending in 0, then you have at least one good car every day. So, the people with means try to have two cars with different number plates. For that reason, the Bogota pico y placa changes the digits every year. So, it is theoretically possible that your good combination may not be that good next year. However, based on my understanding of Bogotá pico y placa, the digits are always in contiguous blocks of 4, so if your two license plates end in 0 and 5, then you are perpetually safe. If my understanding is correct, then that is a limitation of the system, and the numbers should be mixed up more thoroughly. To put in perspective though, that limitation is small as only a limited number of people buy two cars to circumvent the system.
Granted, we would have to call it peak and plate here, but could the concept work? For about 8 months of 2011 I participated in ride share program wherein me and my ride share partner would drive during alternate weeks, to take advantage of the HOV restriction on I-66. The ride share program works as is, and there is even a full slugging system in DC, but if there were more people participating in ride share programs, that would perhaps be easier to find people leaving from and going to same places, and the ride share could really work even better. Participation would of course be almost mandated by peak and plate in DC.
Although WMATA stopped trying to be price-competitive a very long time ago, it is even possible that due to increased ridership, even the metro fares may come down a little. (For a visual on how high metro fares suppresses ridership which raises fares, consider this.)
After a lengthy preamble, here is a question for you: