When making decisions about where to develop their next residential or commercial project, real estate developers should factor in the actual transit times it takes their customers to carry out the tasks of daily living, transit consultant Jarrett Walker said at a presentation to ULI members and staff at the Institute’s Washington, D.C., headquarters last week.

To illustrate his point, Walker, author of the book Human Transit and a blog by the same name, displayed an isochrone map of three different levels of transit times from a hypothetical office location in Portland, Oregon, where he is based. The blue area of the map indicated a 15-minute transit time for running errands or grabbing lunch with coworkers; green indicated 30-minute transit time, what many consider an acceptable commuting time; the red area indicated a 45-minute transit time, appropriate for once-a-week trips.

Related: Walker’s piece for CityLab on All-Day,Abundant Transit

The map, produced with the OpenTripPlanner Analyst mapping tool created by Washington, D.C.–based transportation tech firm Conveyal, illustrates what Walker calls an “abundance of access,” or the “ability of as many people as possible to reach as many destinations as possible as quickly as possible . . . so they have as many real choices and opportunities as possible and are therefore free.”

A critic of tailoring urban planning to motorists, Walker upended the notion that the car is the ultimate symbol of freedom. Freedom, he argued, is the ability to get quickly, safely, and conveniently to where you need to go. He suggested that Conveyal’s mapping tool may be a “good way to measure outcomes,” or, probable commute times,when making real estate purchasing and tenancy decisions. And he hopes that one day every multiple listing service listing of a residential property would include access to this type of mapping tool, not unlike a WalkScore.

Walker, who has a doctorate in humanities and theater arts from Stanford University, has forged a 20-year career as a transit consultant, working with public agencies in North America, Australia, and New Zealand.

An expert on language, Walker tries to make clients and audiences aware of how language choices affect transit policy debates. He views the professional silos from which developers, planners, architects, and transportation officials talk past one another using different definitions of success as the main problem in transit planning today.

“If you spend any time listening to transit debates, you hear a lot of strident certainty,” he said. “Transit debates are incredibly confused because there are a bunch of different outcomes that different people want around the table.”

Walker also cautioned against accepting the status quo as being rooted in fact instead of what it truly is—the consequence of policy decisions influenced by politics, cultural biases, and emotional reasoning. To illustrate his point, he cited Los Angeles, a city known for its gridlock and packed freeways. He questioned the tendency to accept L.A.’s “car culture” at face value.

“Maybe L.A. is a city where given the infrastructure we’ve built, driving a car is [what] gives people options,” he said. “I see no evidence that Los Angeles is a car culture. I see evidence that driving in Los Angeles is the logical thing to do. See the difference?”

Jarrett Walker’s presentation to ULI Triangle in Raleigh, North Carolina is available online.