When Colorado Governor John Hickenlooper was Denver Mayor John Hickenlooper, he learned that more lanes for cars don’t fix congestion — it just enables more cars to fill up the highway.

Hickenlooper got the lesson in “induced demand” from all-star city planner Jeff Speck, the author of Walkable City, in 2004. Speck was in town for the Mayor’s Institute on City Design, a conference where planners shared knowledge with mayors about the basics of good urban design.

The conference happened at around the same time Colorado DOT decided it wanted to widen I-70 in north Denver.

“Mayor Hickenlooper was one of the star pupils,” says Speck. “He was a real delight to work with. In my talk, because I think it’s one of the most important things to understand, I went into great depth about induced demand, as I always do. He understood it, and we haven’t interacted at all since then. I’d rather be having this conversation with him but I’m not the type to reach out to a governor and try to get him to call me back.

Today, Hickenlooper may be the only person who can stop his transportation agency from widening I-70 by four lanes. So far he’s kept his distance from the project, but he’ll have to intercede to prevent a mistake that would scar Denver for generations.

Hickenlooper must be aware that widening I-70 won’t actually solve any problems. Instead, it’s going to burden the city with more traffic, just like the recent expansions of L.A.’s 405 Freeway or Houston’s Katy Freeway.

When Hickenlooper became governor, he inherited CDOT’s archaic plan. Speck says that it’s his responsibility to decide if he wants to invest in smart transportation modes, like transit, or driving, which comes at a much greater cost to society.

“Every major road-building project has a lifespan through several political generations, and each generation has a responsibility to address it based on the latest understanding of best practices,” says Speck. “And our understanding of best practices has changed. For a newer governor to support a decision of an older governor which is based on a logic which has been debunked, it doesn’t seem to me to be prudent.”

“I’m not trying to give the governor a hard time because I haven’t followed state politics in Colorado at all and I don’t know Hickenlooper’s record on these other things,” says Speck. “I know one thing and one thing only which is that he understands induced demand.”

When Hickenlooper was mayor, he championed the massive FasTracks transit expansion. Where is that fervent support of smart transportation policy now?