Atlanta, Georgia: famous for peaches, Coca-Cola, and some of the worst traffic in the world.

In 2017, Atlanta was the eighth most congested city worldwide, clocking in with more hours (70) spent in heavy traffic per year than Las Vegas and Philly combined.  While Atlanta’s traffic has improved in recent years, it has a long way to go ― and I was reminded of that fact while driving to college move-in weekend with my family a few days ago.  While stuck at a standstill at Spaghetti Junction, a twisted mess of interstate highways and exit ramps, we observed how space varied between cars.  Some (more passive) drivers tended to give one or two car lengths of space between them and the next vehicle, while other aggressive ones were almost bumper to bumper.  I’m a budding transportation geek, so the varying distances had me thinking: do we even need stopping space at all?

At first glance, the answer may seem simple.  Yes, of course we need stopping space ― without it, there would be crashes left and right.  But, when I delved deeper into the reasoning behind the extra wiggle room, I discovered it could be eliminated entirely.

The key is uncertainty.  Drivers allot stopping space because they’re uncertain of when the car ahead of them will stop; a longer distance provides more time to react to other drivers and avoid a collision.  If drivers were magically synced so they would all brake or accelerate at the exact right time, vehicles could drive almost bumper to bumper and traffic could be heavily reduced or eliminated entirely.  Of course, different makes and models of cars and larger rides like trucks or buses would be a factor, but the rule stays the same: less uncertainty, less congestion.

In addition to the principal benefit of reduced/no traffic, roadway staples like stoplights, crosswalks, and traffic cops could become obsolete, and the funds saved from their maintenance used to improve road safety and create alternative routes (like overhead bridges) for pedestrians.  As a side note, a scenario like this is obviously impossible, but it’s fun to think through and it could provide insight in other, more useful situations.

I had a realization while thinking through the logistics of removing or reducing stopping space: the scenario visualized above is the theory behind mass transit ― current mass transit systems reduce uncertainty for riders by having preset routes, schedules, and stations.  The reason why the world hasn’t switched entirely to shared transport is that modern systems give users reduced choice, but lower cost and transit time.

The subway can’t take you from your front porch to your office steps, but they can take you from station A to station B ― mass transit is more efficient, but individualized transit is more convenient.  And for most, the convenience of individualized transportation outweighs other benefits of mass transit, so stopping space persists.

Eventually, mass transit may acquire the range to go door to door, and stopping space could be a thing of the past.  But until then, there will always be standstills at Spaghetti Junction.