Skip to Content
Streetsblog New York City home
Streetsblog New York City home
Log In
Streetsblog

The Problem With Designing Streets for Peak Hour Traffic

If St. Paul widens this road to make it work better two hours a day, it will work worse the remaining 22 hours for the people who live nearby. Photo: Google Maps via Streets.mn
If St. Paul widens this intersection to make traffic move faster for a few hours each weekday, it's going to work worse all the time for everyone who lives nearby. Photo: Google Maps via Streets.mn
false

When engineers make decisions about streets, they tend to emphasize the "peak hour" -- the morning and evening rush when traffic is at its most intense. For the most part, city streets are still designed to move motor vehicles during this relatively short period of time, to the detriment of people outside of cars -- i.e. the people who live in the neighborhood.

Bill Lindeke at Streets.mn has been thinking over the implications of this approach to street design. He uses an example in Saint Paul, where the county is considering adding a turn lane to reduce rush hour delay:

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” [level of service] 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 trying to cross the street.

Lindeke says that the tools engineers are using to evaluate the situation have some serious drawbacks:

The seemingly neutral LOS charts in an engineering study are actually a highly reductive view of the world, epistemological blinders that pay attention only to cars traveling at certain times of day. Like any science, a traffic study is making assumptions about what’s valued and what counts, and for generations we’ve acted under the assumption that rush hour is the most important time of day. And that leaves a lot of other factors out of the picture.

Part of the problem is the lack of good data about how many people are walking or biking, or how the road widening might affect the quality of life of nearby residents, Lindeke says. To produce better results, he points to an idea from the National Association of City Transportation Officials, which recommends factoring in other modes besides driving and other times of day besides the peak hour when making decisions about the allocation of street space.

Elsewhere on the Network today: Vibrant Bay Area notes that wealthy suburbs are almost universally dependent on cities with lower average incomes, and that is especially true in Detroit. And Free Range Kids says President Obama is about to sign the "first federal free-range legislation" protecting parents' right to allow their child to walk to school.

Stay in touch

Sign up for our free newsletter

More from Streetsblog New York City

Power Play: City Can Now Padlock Businesses Violating Lithium-Ion Battery Rules

The city can now forcibly close repeat offender shops that sell illegal lithium-ion batteries. But will it?

October 10, 2024

Study: How The Last Three Presidents Helped Shape Our Local Transportation Landscapes

A deep dive on one of America's largest discretionary grant programs reveals the kind of transportation projects prioritized by the last three presidential administrations. What does it mean for the future?

October 10, 2024

Thursday’s Headlines: Duggan Gets the Story Edition

Our version of the BQE story was better than those written by people at the DOT's invite-only presser.

October 10, 2024

City Delays Road Diet Under BQE Despite Hyping Its ‘Reconnect Communities’ Effort

Officials touted new concepts to improve the streetscape around the BQE — but was wavering on plans to do just that on Third Avenue in Sunset Park, Streetsblog has learned.

October 9, 2024

A Father Speaks: Here’s Why The Speed Limit Must Be 20 MPH Everywhere

At an event on Wednesday, no one was more eloquent than the spotlight-avoiding father of the boy for whom Sammy's Law is named.

October 9, 2024
See all posts