Study highlights importance of travel time as a metric

By Eric Sundquist

As commute times increase, married women work fewer hours or even drop out of the workforce according to a forthcoming article in the Journal of Urban Economics. The finding, summarized for a general audience recently in Atlantic Cities, helps explain differences in women’s workforce participation across various metro areas.

This insight may seem less important to transportation practice than to labor-market studies. But in its focus on travel time as a driver of economic outcomes, the article has clear relevance to transportation agencies that are wrestling with setting meaningful, outcome-based performance measures.

The paper, by Dan A. Black of the University of Chicago and others, is only the latest to look at economic outcomes of travel time. Questions such as whether people have a fixed “budget” for travel time and how they value their time spent traveling are mainstays of the literature, and of practice. For example, value of time is central to mode-choice modeling. The idea is that time spent traveling is a cost, and travelers would prefer to reach their destinations with less time cost, i.e., in less time.

What this literature does not address is precisely what transportation practice usually focuses on: speed of travel, which often is framed in terms of “delay”, or the difference between observed traffic speeds and some ideal speed. The literature focuses on time rather than delay for the precise reason that it matters how long it takes to get somewhere, not how fast the traveler is going on the way.