I had never considered this question before reading Tom Vanderbilt's book Traffic nor had I considered the strong emotions that two very different segments of society feel towards merging. According to Vanderbuilt's book people generally behave in two ways when alerted by road signage that lanes merge ahead. On one side are the early mergers, who quickly move over into the merged traffic lane. On the opposing side are the late mergers who travel until the very end of the usable roadway before merging. Early mergers believe that all traffic woes would be resolved if everyone merged into the open lane as soon as signage appears. The late mergers feel that the road should be utilized to maximum efficiency "why should an entirely good lane go to waste?!" Traffic congestion results from the confrontation between these two groups at the final merging opportunity when many early mergers use the opportunity to play traffic cop and block what they call "cheaters" from entering their lane. Vanderbilt's conclusion and that of many traffic engineers is that late merging is indeed the best practice and the resulting zipper (alternating merge) minimizes congestion. Unfortunately due to the "friction" of the two opposing mindsets in our society we can never achieve that efficiency and thus the alleviation of traffic congestion.
Tom Vanderbilt's book Traffic offers a rigorously researched and thoroughly intellectual analysis of our human behavior on our roadways. His book neatly and clearly explores the many ways drivers behave on our elegantly designed roadways and behind the wheel of our high tech cars.
Traffic combines countless studies with interviews and anecdotal stories to provide a book with a foundation of sound conclusions that remains pretty fun to read.
Among the many nuggets of knowledge from this book:
- There are 56 ways you can hit someone or something in an intersection. 32 of these involve a car and 24 involve pedestrians. There's some food for thought as I'm driving on the Boulevard.
- Roundabouts are, despite many complaints of terror, the safest form of intersection typically reducing fatalities to 0. At a roundabout there are only 8 ways to hit something or somebody and the speeds at which the collision occurs ensures it is merely a minor crash.
- My next car is definitely going to have Adaptive Cruise Control. According to a study by GM just a handful of cars in a traffic jam operating ACC can cause the congestion to dissipate by eliminating the stop and go braking and maintaining a constant distance between vehicles.
- The safest railroad crossings are the ones where the view of the tracks is obscured by trees. As it turns out humans are terrible at judging distance and speed, especially when it comes to large objects like trains. Studies show that grade level railroad crossings that have a clear line of sight down the tracks actually result in more fatalities as drivers are more likely to attempt an unsafe crossing. The drivers base their poor judgment on the optical illusion that a large object (locomotive) appears to be moving at a slow speed (but not really).
- Why does the other lane always seem faster than mine? Vanderbilt covers the human psychology behind this and the nature of traffic congestion. According to his research congestion in each lane behaves almost like an accordion with each lane behaving independently, but at very similar rates of compression and expansion. While the lane next to yours may be moving faster (in a state of expansion), yours may still be stalled in a state of compression.
For my northern Virginia friends who spend a good portion of their lives in vehicles on the highways around DC I highly recommend this book. It offers, if nothing else, a fascinating insight into the human behaviors that cause traffic nightmares of daily life in a large metropolitan area and some of the policy, design, engineering and behavioral changes that could remedy these frustrations.
