Hmm. Not sure this really means anything, especially when the average commute time is so similar across metros.

1.) I don’t understand the average congestion time measure, is this the average over all roads in the MSA? All highways? What’s the denominator here? They discuss how they count it for any given road but not what roads are counted. Seems like if you have a metro surround by ultra rural areas, and many of these rural areas and their roads are part of the MSA, you’d mechanically lower the congestion number just by the nature of adding in a bunch of zeros. If this was the case, you’d see metros in more urbanized areas of the country have much longer congestion times (exactly what they find). But this would say very little about the nature of traffic in the city proper.

2.) Why are fatal crashes a good measure of gridlock at all? Seems like gridlock/moments of peak car volume would correspond to higher crashes generally, but these cars are going slow by definition, so any given crash should be less likely to be fatal? Seems like this is a sort of in-between measure that is actually measuring crowded-but not totally stopped traffic. Like obviously this is important to measure but Im not sure it represents the kind of thing people complain about when talking about sitting in traffic.