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Peak-hour myopia: Why we're doomed by rush hour traffic



Larding up any Department of Transportation work plan are projects that cost millions, but do little to improve our quality of life. (Exhibit A: The $100 million + Bruce B. Downs expansion project -- all that money and it won't even ease congestion). 

But writing for, a transportation and land use blog in Minnesota, Bill Lindeke, captures just how doomed we are because of the way society views transportation problems.

If a road is jammed with congestion, well, we must fix the road by widening it, right?

Lindeke points out that our flawed thinking begins and ends with peak rush hour. It's those two hours in the morning and the two hours in the late afternoon that overload our roads. 

Writes Lindeke:

If you combine the two "peak hours" (giving them 2-hour time slots), you end up with 4 hours of the 24-hour day. That leaves 20-hours of the day that are "off peak", times when the road will be "overbuilt" for the amount of traffic that it has.

Basically, transportation planners are always faced with a choice here: Do you give design priority to the people using the street for those 4 hours of the day at the expense of the people that "use" the street for the other 20 hours? 

Oddly, we have data that counts the number of cars that use roads, but nobody counts pedestrians or cyclists, Lindeke notes.

Nobody carefully surveys nearby neighbors about how traffic speeds affect their everyday lives. We don't really know how many people are using the streets or sidewalks on foot, bike, or experiencing the street from their front yards or porches.

The result is that too many roads are designed (and expanded) to handle rush hour traffic that is only an issue for four hours out of every day.

And that has consequences. Lindeke provides this example from Saint Paul:

An intersection, Lexington Parkway and Randolph Avenue, that is by an urban freeway and a Trader Joe's. Because of the popularity of cheap cheese, rush hour traffic has been getting worse at the corner for a few years  (or so I am told). As the street is being reconstructed, the County did a study that recommended adding a turn lane, which would address rush-hour "level of service" (LOS) in two ways: decreasing "stacking" by adding the storage capacity of an extra lane, and by allowing cars to more easily turn on red around the corner. 

By making this change, the Ramsey County study projects that the average car will save a few seconds of time stuck in traffic. For example, according to the model the proposed layout would subtract 20 seconds of delay for Northbound cars while adding a 5 seconds to Southbound cars.

The key thing, though, is that these time savings only occur during the peak hour. For the rest of the day, when the "capacity constraint" isn't constraining much of anything, the impact on drivers would be negligible.

Meanwhile, for the entire day, the intersection would have worse "LOS" for everyone else, especially people on foot trying to cross the street. Adding a turn lane, widening the street, or adding a thru lane (which are three of the options) would increase speeds at the intersection at all times of the day and night, eroding safety for neighbors and anyone on foot.

It's the kind of tradeoff we just don't talk about here in Tampa Bay. Sure, add that turn lane so cars can get through an intersection faster. Just know that by widening the intersection or adding a turn lane, you're increasing the speeds of the cars the rest of the day, making it that much harder for pedestrians or cyclists to use the road as well.

Just wait until Bruce B. Downs is finished and you'll see. But if you're on foot, you better run.

[Last modified: Monday, December 21, 2015 6:10pm]


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