The number of pedestrian deaths in the U.S. reached a nearly 30-year high in 2018, according to a report being released Thursday that points to smartphone distraction and the growing prevalence of SUVs as possible factors.

An estimated 6,227 people died on foot from car crashes nationwide last year, the most since 1990, according to the report. Pedestrian deaths now account for about 16% of motor-vehicle crash deaths, up from 12% a decade ago. In that span, all other traffic deaths grew by less than 5%.

“We’re...