Before and After Carpool Lanes

Josh Cohen reports on a study that evaluated the outcomes of Jakarta's "three-in-one" high occupancy vehicle (HOV) lane policy, implemented between 2003 and 2016. The law requires "private vehicles to carry three people to drive on the main roads in Jakarta’s central business district, from 7-10am and 4.30-7pm," explains Cohen.

"Many believed the policy was ineffective and felt that opening the restricted road to all would help traffic flow better, but a new study published in the journal Science found the opposite to be true," writes Cohen. "Hanna and MIT researchers Gabriel Kreindler and Benjamin A Olken discovered traffic congestion worsened after Jakarta lawmakers abruptly eliminated the HOV policy in April 2016."

Though controversy surrounded "'jockeys' who would stand just outside the enforcement area and offer to join a single-occupancy vehicle for a fee so the driver could enter the three-in-one zone," while the law was in place, the study found that there were enough people staying out of their cars to outweigh the number of scofflaws skirting the rules. Once all of those people stopped driving in carpools, "the newly unrestricted main roads were unable to accommodate the increase in vehicles from people no longer car-pooling."