How Autonomous Cars Could Lead To Even Worse Traffic

Unless we also give up car ownership, things are going to get very crowded as empty cars try to get home.

Picture the scene. It’s a typical morning commute, marked by traffic congestion and frustration. Except this time it’s not drivers complaining to each other about the traffic, it’s autonomous cars. That sounds ridiculous, but it is the current trajectory for the future of personal mobility.


The allure of Elon Musk’s vision for autonomous vehicles is understandable, particularly with proclamations that “within two years you’ll be able to summon your car from across the country,” all of the obvious safety benefits to come, and all the cool tech that goes with that.

However, a missing dimension when we paint this vision is our daily pattern of car utilization. The efficiency of our transportation system doesn’t improve simply because cars will drive themselves more efficiently than we can. A predictable tidal wave of traffic congestion will still hit all of our cities every weekday morning and evening. In fact, it will get worse.

The pervasive wisdom is that autonomous cars will appear and disappear as we wish, wherever we go. Our primary transportation resource (256 million cars and counting) will essentially live in the cloud. Personalized mobility on demand. Most articles written on the subject portray a transportation system that is seamlessly efficient, the ultimate product of the sharing economy. And a recent article in the Wall Street Journal explains that “25 years from now, the only people still owning cars will be hobbyists, hot-rodders, and flat-earth dissenters.” The common perception is, therefore, that this version of the future is inevitable. It is not.

Today, the average occupancy of a car is 1.1 people at commute time. That’s the reason you waste a week of your time every year simply sitting in traffic. Research has shown that even a small (2% to 5%) reduction in traffic volumes can lead to a giant reduction in total traffic delay (25% to 27%). It’s a nonlinear problem. And yet, instead of our cities competing on commute-time occupancy scores for federal transportation funding to mitigate traffic volumes, we continue to invest $80 billion annually on new roads and $87 billion in wasted fuel and lost productivity. Not to mention the harmful impact on local air quality, with the American Lung Association reporting that almost half of us are breathing air polluted enough to make us sick.

At the same time as making these investments, we celebrate the arrival of the autonomous car as the solution, with President Obama recently announcing $4 billion over the next 10 years on autonomous vehicle technology. That $4 billion is largely earmarked for safety features, a very worthy cause, which may well also result in enabling cars to be more tightly packed in traffic. However, any potential improvements in traffic flow that nonhuman drivers will allow will be negated by that nonlinear nature of traffic congestion. And because the driverless car of the future will be riderless a large portion of the time, as it moves to and from the “cloud,” occupancy rates will be driven down even further–and overall traffic volume will increase, thereby leading to a significant increase in overall traffic delay.

Today, the average American household has 2.28 cars, each one sitting idle 95% of the time. For most Americans, there is no alternative. Most people live and work in America’s suburbs and exurbs; they don’t take Uber to get to work, and they don’t live near a transit stop. They’ve been left behind by a downtown mindset in mobility innovation and neglected in our collective vision for shared autonomous cars, if we even have one. A recent MIT study shows that the entire population of Singapore could be served by approximately one-third of the total number of passenger vehicles currently in operation –but getting to that point requires a giant collaborative effort, fueled by Tesla-levels of iteration and inspiration, and ultimately leading to societal behavior change.


There is, therefore, an urgent and fundamental need to change our long-established car utilization patterns. The same (high-occupancy) car that takes you and your neighbors to work should be the same car that takes your colleagues to off-site appointments during the day, and your family on a shopping trip in the evening.

The same urgency that Silicon Valley applies to summoning a car from 3,000 miles away has to be applied to the logistics of ensuring that cars are shared and filled efficiently throughout the day. If we don’t change course, we’re heading toward a future in which zero-occupancy vehicles further clog up our already congested roads. And nothing is more likely to trigger robots taking over the planet than having robot cars stuck in traffic every day, right?

Emmett Murphy is chief product officer at Carma.