Jakarta study finds HOV policy reduced number of cars in city
7 July 2017
In March 2016, Jakarta, Indonesia, with a population of more than 30 million, abruptly ended a high-occupancy vehicle (HOV) policy that required three passengers in a car during peak hours. The sudden halt provided a team from Harvard and MIT with valuable insights into how carpooling affects traffic flow within the megacity.
In a paper published in Science, the team reported that after the policy was abruptly abandoned, delays rose from 2.1 to 3.1 minutes per kilometer (min/km) in the morning peak (a 46% increase) and from 2.8 to 5.3 min/km (an 87% increase) in the evening peak.
The lifting of the policy led to worse traffic throughout the city, even on roads that had never been restricted or at times when restrictions had never been in place. In short, the team found that HOV policies can greatly improve traffic conditions.
Within 48 hours of the cancellation announcement, the research team began querying Google Maps to collect data on traffic on major HOV roads, as well as two alternate roads that ran parallel to the HOV roads; they continued to collect and analyze traffic data as the HOV policy was lifted several days later.
In addition to the significant increases in travel time along the previously designated HOV roads, but along the parallel roads as well. Increases in travel time were also observed outside of rush hour.