Route 24 in Nassau County and Route 25 in Suffolk County are among roads on Long Island with the most vehicular accidents involving pedestrians and bicyclists, according to an annual survey released Thursday by a transportation advocacy group.

And for the first time in its report, the nonprofit Tri-State Transportation Campaign calculated crashes per mile of road to account for the length of the road. The campaign also had previously reported only crashes involving pedestrian fatalities, but this year included injuries to bicyclists.

There were 256 motor vehicle crashes involving pedestrians or bicyclists in the three-year period from 2014 to 2016 on State Route 24 (also known as Hempstead Turnpike, Fulton Avenue or Conklin Street), the watchdog group said.

Six of those crashes resulted in a death of a pedestrian or bicyclist, and there were 238 reported injuries, according to the report ‘‘We’re Walking (and Biking) Here.’’

State Route 25 in Suffolk County (also known as Middle Country Road, Jericho Turnpike or Front Street) had 224 crashes from 2014 to 2016, resulting in nine fatalities and 206 injuries to pedestrians or bicyclists, the group said.

Both Routes 24 and 25 are multilane roads with a high volume of traffic and have residential and commercial stretches.

advertisement | advertise on newsday

“One dominant trend is that crashes are concentrated on Long Island’s major thoroughfares, which are classified as arterial roadways,” said Tri-State Transportation Campaign Executive Director Veronica Vanterpool. “These arterials are lined with places where people live, work and shop, but they’re designed to move cars and trucks quickly from place to place. As the research shows, arterials don’t have a very good safety record, especially for people walking and riding bikes.”

A bicyclist riding in the center of Route 110 was struck by a car and critically injured Wednesday night at the intersection with Broadway in Huntington Station, Suffolk County police said.

Other roads on Long Island with a large number of accidents included Merrick Road in Nassau, with 237 crashes and five fatalities, and Route 110, (also known as New York Avenue, Walt Whitman Road and Broadway) with 141 crashes and 10 fatalities, the group said.

The Suffolk stretch of Sunrise Highway had 94 crashes and 9 fatalities, while the Nassau section of Sunrise Highway had 146 crashes and 11 fatalities, the group said.

Among roads on the Island with the most crashes, Nassau Road in Nassau County had 36.6 per mile, the campaign said. In Suffolk, Route 110 had 9.7 per mile, the group said.