The congestion relief benefit of public transit: evidence from Rome

We estimate the effect of public transport supply on travel times of motor-vehicle and bus users in Rome, Italy. We apply a quasi-experimental methodology exploiting hourly information on public transport service reductions during strikes. We find that a ten-percentage point reduction in public transit supply increases the travel time of motor-vehicles by about 1.6 percent in the morning peak. The effect on bus travel time is similar. The congestion-relief benefit of public transport is thus sizeable and bus travel time gains account for an important share of it.