Here's an explanation from Streetsblog LA:
A leading pedestrian interval, or LPI, lights up the pedestrian signal a few seconds before vehicular traffic gets the green. This gives pedestrians a head start into the intersection and makes it less likely that they will be hit by vehicles turning into the crosswalk. LPI's are also known by their sassier nickname, Pedestrian Head Start. But in my view the best variation on what LPI stands for comes from Christine Berthet of the Hell's Kitchen Neighborhood Association, who proposes "Life Preserving Interval."Head over to Streetsblog for a great video demonstrating the idea.
Implementing this on Brand Blvd. between Colorado and California would certainly make the near-daily walk to Porto's less stressful.