One more tidbit from last Friday’s Regional Plan Association shindig: During the Q&A session at the “Cars vs. Bikes vs. Pedestrians” panel (a title that seemed unnecessarily provocative to moderator Trent Lethco, RPA board member and transportation consultant with engineering firm Arup, until he concluded that it “reflects realities”), I asked about leading pedestrian intervals.

An LPI, also known informally as a “Life Preserving Interval,” lets pedestrians enter the crosswalk before turning drivers get a green signal. It seems like a cheap and effective way to reduce injuries and deaths caused by turning drivers, but I wondered if there must be a hidden downside, since they are not more widely used.

Sam Schwartz answered first. He said LPIs were invented in New York, in the 1980s, and that they have a limited impact on vehicular capacity. Jon Orcutt said DOT has been adding LPIs at more intersections (watch the Streetfilm for LPI locations circa 2008) and “would like to get to the point where it’s the default.”