Treating Roads Like Rails

The changes that transform a bus route into B.R.T. are small but add up, making buses fast, frequent and reliable.

■ Buses are assigned their own dedicated lanes or roads. They are scheduled to arrive frequently, with a maximum of 15 minutes between buses, so that riders can rely on catching one quickly.

■ Separate traffic signals prioritize buses, which eliminates lingering at red lights.

■ Passengers pay before boarding and enter through every door, speeding up the process.

■ Stops look substantial, with accessible shelters and seating. Real-time bus arrival information is displayed.

The model that many experts reference is the TransMilenio system in Bogotá, Colombia. The citywide system consists of more than 70 miles of exclusive lanes and roadways, with thousands of dedicated buses that carry more than two million people per day.

But two decades in, the TransMilenio has become a victim of lack of continued investment — and of its own success — leading to crowded buses and an overwhelmed system. Nevertheless, getting around Bogotá without it would seem unthinkable now.

Planners in South America took advantage of existing wide boulevards with overpasses and limited intersections to build large B.R.T. systems like the TransMilenio,

said Christof Spieler, an urban planner and a lecturer at Rice University in Houston. “That’s a very difficult thing to implement in the typical U.S. city.”

Rapid bus systems in the U.S. often omit some of the features of B.R.T. that experts say are essential, like continuous dedicated lanes, off-board payment or priority at traffic lights. The Institute for Transportation and Development Policy, a nonprofit transit organization that developed a B.R.T. standard and ranking system, does not consider these stripped-down implementations to be “true B.R.T.”

But even imperfect systems can be a big improvement, especially in midsize cities that have relied solely on buses in traffic and where, Spieler said, “there hadn’t previously been any liftoff.”