The Relationship Between Carpool Policy and Traffic
An experiment conducted by economists from Harvard and MIT was carried out in Indonesia following an announcement that the High Occupancy Vehicle (HOV) policy in the city of Jakarta was ending. According to the city officials, the system was open to abuse through “professional passengers”, people that would ride in one’s car for pay to fit the carpool lane limit and avoid traffic. The economists came to a surprising conclusion after studying traffic patterns before and after the HOV policy was revoked—traffic got worse.
The end of the HOV policy for Jakarta essentially acts as adding a new lane to a highway. Whereas before the lane was only open to a select few people, now any person can use it. This might make it seem as though the opening of the lane should cause traffic to decrease, as more space on the road means more drivers the road can accommodate. There are certain aspects in that thinking that are ignored which likely lead to the results found.
- Ending the HOV policy takes away the incentive to carpool. When the HOV policy is removed and the lane is opened up to everyone, those drivers/passengers that were previously riding together now have no incentive to do so. Instead, they may take their own vehicles and in effect increase the total number of vehicles on the road increasing traffic.
- People no longer had incentive to stay off the road during HOV hours. Whereas previously, single drivers may decide to delay travel until after the HOV policy no longer applied, now those same drivers may decide to travel during peak hours as they see all lanes being open to them. Additionally, even if they wait, more drivers on the road in general could mean higher traffic times for longer periods.
- With more people bringing their cars to work or wherever they were travelling to, they now had the means to travel throughout the day in addition to their initial commute. As was observed, traffic got worse in peak and off-peak times. Now, the new drivers could use their car to get lunch, or to run errands or any other activity that might cause them to get on the road during off-peak hours.
This article relates in some ways to game theory that we discussed in class. For instance, when the HOV policy got taken away, traffic also got worse on roads that didn’t previously have HOV lanes. Consider a driver in this “game”. That driver may decide to take a side road during his travels home. However, as mentioned above, there were more people using their cars. This means, while taking the alternate route may be the new Nash equilibrium for the new game with more drivers and no HOV, this game’s best time can still be less than the previous game. Additionally, the amount of drivers being added to the system may cause the Nash equilibrium to occur when drivers spread their routes out, causing traffic to occur all throughout the city. Perhaps the carpool system truly gives the best payoff–both for drivers and “professional passengers”.