Here's a thought provoking talk on traffic by Tom Vanderbilt.

Interesting section at minute 8 where he explains why cars tend to travel in bunches and why it's so difficult to maintain a steady speed. I wonder what even a small population of driverless cars would do to impact this. I bet you'd see more non-driverless cars going "steady"

Yeah. I agree, but I'm guessing that it would only take one human driver to cause a backwards wave in the traffic.

What he left out was the impact that trucks have in slowing down traffic. My express bus that takes me into Manhattan uses the turnpike and I see all the slow moving trucks going in the opposite direction holding up traffic as they climb the ramp at 10 miles per hour! You bet that slows down traffic and if you put thousands of them on the road, you'll never be able to fix rush hour traffic.

I visited San Francisco once and was amazed at how traffic would back up on mildly foggy days. Never failed. Any variable will cause chaos.

When I was in southern California, I was surprised how much a light rainfall would slow things down. Here in Michigan, traffic goes at a pretty good clip in heavy snowfall, and rain doesn't slow it down at all.

I drive too much so I get to see traffic in action. Driverless cars would certainly improve traffic flows, another stray thought was driverless trucks could be run at low peak traffic times and could be routed to avoid peak traffic areas, also driverless trucks could run 24/7 and not be restricted by the required rest periods needed by human drivers.

In many hilly regions they have truck lanes and restrict trucks from the left lane to allow the lighter vehicles to travel through, however they are quite often thwarted by functionally illiterate truck drivers and people in cars not driving the speed limit. Another human ploy that causes traffic slowdowns in urban areas is the idiot that comes down the ramp and immediately merges to the far left lane causing the cars traveling at the speed limit to slam on brakes to keep from hitting them, then everybody has to get back up to speed, eventually as the traffic load increases this causes the slowdowns, that cause traffic backups.

I wonder how driverless cars would perform in heavy fog, rain and other inclement weather?

Aaron

I read his book several years ago; OUTSTANDING!

Here was an interesting test mentioned in the book: selective attention test - YouTube

That's a good thing. Here in PA and across all the northern states that has I-80 running through it, fog and snow that produces 0 visibility conditions doesn't slow anyone down a bit. They just keep trucking along at 70-80 mph straight into the 30 car pile-ups. Every snowstorm there is at least 1 many car pile-up between PA and Indiana on I-80.

I got caught on I-80 in one of these 0 visibility snowstorms. Had to get off because I couldn't see past my wipers, slowed down, and had cars flying around me at full speed. I'm no slouchh in the snow and can drive through just about anything, but I call it quits if I can't see the hood of my car and others around me keep on going at 80 mph.

He states in his book that variations in speed among drivers of vehicles is not a significant source of crashes or congestion as is popularly believed. You should read the book.

It was a good book. Vanderbilt also has a lot of recent articles on the internet--Slate.com, Atlantic Cities, Youtube, his own blog, and so forth. He is very insightful about traffic, transportation, automobiles, and alternatives to automobiles.

The irony is that when traffic builds up to the point of critical flow-density, such backwards waves are needed to allow space to grow between the vehicles. Traffic jams serve as bottlenecks that allow traffic in front of the jam to clear. Drivers accelerating out of the front of a traffic jam have room to drive precisely because the traffic jam held them back to allow that room to form.

People don't seem to realize that any bottlenecks clear the road in front of them in this way. Left-turn arrows that hold back left-turning traffic, for example, perform such a function. So do long traffic signals. So do accidents. So does narrowing a road down a lane before adding the lane back after some distance (literally a bottleneck). Remove all bottlenecks from traffic and you will eventually end up with one huge traffic jam.

Driverless cars could actually achieve a perfect singularity of a unified traffic jam if they were all steady enough and homogenously programmed. You would just need to keep adding one at a time to the roads until they all reach their simultaneous operating limitations. At that point, the backward wave would be total and everything would stop.

Hopefully at that point there will be a bike lane and sidewalks for everyone to get by the vast sea of frozen motor-traffic.