Autonomous car adoption could increase downtown traffic

16 July 2018 5 min. read

A new report finds that autonomous vehicle rollout will drive the increasing adoption of ‘mobility-on-demand’ options – robo-taxis, ridesharing, and autonomous minibuses. A study of Boston found that the mode of transport will increase to 30% of rides in the city area. However, mobility-on-demand’s increasing substitution for short mass transit trips may lead to increased congestion in the downtown core.

Autonomous vehicles (AVs) are on the cusp of making a breakthrough into the mainstream. Today, there are more than 100 AV pilot projects taking place around the world, including high-profile projects from Google and Uber. With rapidly expanding pilots and technological advances, commercial AV-taxi services are expected to already be in place in a number of large cities this year. The greatest revolution in personal mobility since the invention of the car is nearly upon us.

With AVs nearly on the scene, there is a real need by the public and private sector to understand how the technology might change the way people move in urban centres. A recent joint report from The Boston Consulting Group and the World Economic Forum examined how AVs would impact transportation in one city, namely Boston. Over the last three years, the partners researched consumer sentiment and conducted impact studies using active trials as well as city-wide traffic simulations.Openness to AVs and projected shift in transportation modesThe report’s survey results found that global consumers are open to adopting AVs, with 60% of respondents saying that they would ride in an AV. Acceptance, however, varied from 36% in Japan and 40% in the Netherlands, to 75% and 85% in China and India, respectively. The report linked the lower acceptance in countries like Japan, Holland, and Germany to a longer established car culture than in China and India, where the car market is still developing. Another factor was higher levels of congestion in cities like Mumbai and Beijing predisposing consumers in those markets to be more open to the prospect of AVs.

The report’s analysis projects that the advent of AVs will drive a significant shift to ‘mobility on-demand’ options (taxi/ride-hailing, autonomous taxi/shared taxi, autonomous minibus), growing the segment from 7% currently in the Greater Boston Area to 30% in the future. 87% of mobility on-demand will be composed of AVs, according to the analysis.

The switch to on-demand will cause mass-transit ridership to decline heavily in urban areas (-14%) because of the cost-competitiveness and convenience of autonomous ride-sharing. Mobility on-demand will account for 40% of trips in urban Boston, reducing personal car trips by the same amount as mass transit (also -14%).

The research found that in suburban areas, mobility on-demand will mainly replace personal car trips. The former will increase 21 points to 26%, while the latter will drop 23 points to 42%. Meanwhile, mass transit use will actually rise in suburban areas of the city, growing 2 points to 32%. Some of this has to do with the fact that on-demand AV trips are cheaper the shorter the trip is (which is part of what makes it more attractive to urbanites). For suburban travelers who have a longer average trip, especially if they’re commuting to work, a fixed-cost mass transit ride may make more sense economically.Disaggregating travel time impactBCG and the WEF then used an advanced simulation model developed by analytics division BCG GAMMA to examine the impacts of AV adoption in Boston. The model projected a 15% decrease in the number of vehicles on the road, mainly caused by the shift from personal cars to mobility-on-demand. The model also, however, projected a 16% increase in the distance traveled by vehicles resulting from the added trips of on-demand vehicles to pick up and drop off passengers, and the empty miles driven in between passenger rides. As such, it’s imperative that AV cars of the future are ‘eco-friendly,’ otherwise they may contribute to higher emission levels from transport.

The model found a significant decrease in the amount of parking space needed (48%) because of the shift to mobility-on-demand, wherein the car will just go on to its next passenger. The model also found a throughput (in this case, traffic flow efficiency) gain of 6.3% with 37.5% AV adoption. Increased efficiency derives from a lack of human driving behaviours like rubbernecking, poor lane merging, double parking, etc.

According to BCG GAMMA’s model, travel times in Boston would improve by 4% in the future. However, the introduction of shared AVs will actually increase congestion and travel times in the downtown core by 5.5%, as travelers substitute mobility-on-demand for short public transit trips – clogging the roads with more vehicles in the process. In suburban Brighton and Allston, on the other hand, shared AVs will mostly replace personal cars rather than public transit, reducing travel times by 12%. Thus, the roll-out of AVs will seem to give unequal congestion relief in suburban and urban boroughs.

The report offers a few options to mitigate the negative urban congestion effects. One suggestion is to create an occupancy-based pricing scheme, which makes travelling alone more expensive – whether in a personal car or a robo-taxi. Making single-person rides more expensive would shift travelers to mass transit and shared taxis and minibuses.

With almost 50% less parking needed, cities could also convert street parking to additional lanes and ease congestion. In the report’s estimation, 20% of on-street parking in Boston could be leveraged for conversion to peak-hour driving lanes.