Try to cross most Boston intersections and you know the drill: Press the button — and wait. The standard in Boston has been for the walk signal to come up only after cars get their green. 

For Brendan Kearney of the advocacy group WalkBoston, that’s a problem.

“I shouldn’t walk up to an intersection, wait my turn, then realize once the traffic starts going the other direction that I was supposed to push a button, then have to wait another whole cycle,” he said.

To Kearney, the system is potentially dangerous because if people have to wait too long, they’ll decide the buttons don’t work and cross against the light.

In Cambridge, there’s a different approach. Like in many cities, the walk signals there come on automatically with the green light, and there’s no need to push a button.

“We try to have as few push buttons as possible in the city of Cambridge,” said Cara Seiderman, the city’s transportation program manager. The city also has something called the leading pedestrian interval, or LPI, a safety measure that allows “people to get a head start as they are crossing the street,” Seiderman said.

It works by having the walk signal come on three to seven seconds before the green, giving pedestrians control of the intersection ahead of turning cars. A New York study cited by WalkBoston shows that the technique leads to 60 percent fewer accidents. While Cambridge has been using LPI for more than 20 years, Boston has hesitated — until now.

After a cyclist was killed by a turning semi in the Back Bay at the intersection of Beacon Street and Massachusetts Avenue in 2015, Boston officials began installing devices to slow down traffic at the corner. This summer, walk signals with a leading pedestrian interval were installed there, as well as at all intersections with Massachusetts Avenue between Beacon Street and Huntington Avenue.

Boston Transportation Commissioner Gina Fiandaca said the city’s Vision Zero campaign to eliminate pedestrian deaths was one reason for the signal change. 

“We launched our Vision Zero campaign about a year and a half ago in Boston, so that really was the impetus of implementing leading pedestrian intervals at pedestrian crossways,” Fiandaca said.

But, she added, LPI’s aren’t the solution for all intersections, and Boston isn’t ready to roll them out citywide.

The most important thing for drivers and pedestrians to do is pay attention.

Correction: A previous version of this story incorrectly attributed this last statement to Fiandaca. This statement is the author's.