[hnrandom]

>Road signs commonly ask you to use both lanes up to the point of the bottleneck. That’s reasonable advice, but it’s not going to get anyone home faster.

If you simply kept reading:

>This is good because it is less likely to affect other traffic by spilling out onto onramps and surface roads. Also maybe there’s someone on the highway who’s planning to exit 3 miles before the bottleneck. If the backup is 2 miles instead of 4 miles, that person doesn’t have to wait in traffic.

[ynniv]

His point is a little different: that someone exiting the highway might exit before reaching the traffic if the line were shorter. My point is that a line on an exit ramp which reaches back onto the highway will cause additional traffic for everyone on the highway. Since his model doesn't take traffic-causing-traffic into account, he never reaches my conclusion.

Exit lines are particularly costly because adjacent lanes of traffic generally only sustain a 10MPH difference in speed. Once the right lane is stopped, a 4 lane highway has a maximum safe speed of 30MPH in the left hand lane. This reduces the flow capacity of the highway and may cause the left lane to lock up because left lane drivers get frustrated at slow speeds and are the more likely to tailgate and cause traffic waves.

His model also is only concerned with the self: "can I reach my goal any faster", and he reaches the mostly correct conclusion that he basically cannot (even though avoiding traffic waves by driving in the rightmost non-exit lane would help him significantly). He does not appear to value his contribution to the delay of the people behind him, which is where all the really interesting conclusions are found, including the reason why traffic wave busting is beneficial.