A new study has found some protected bike lanes are leaving cyclists vulnerable to injury.

The Insurance Institute for Highway Safety (IIHS) looked at the risks associated with different types of cycling infrastructure, including protected bike lanes which are separated from vehicles by a physical barrier such as parked cars, a curb, landscaping or posts.

According to the study, cyclists on street-level protected bike lanes were more likely to suffer an injury than those riding on a conventional bike lane.

Researchers said the surprise findings could be because protected lanes tend to be found on busier roads.

“A cyclist on a protected lane at street level is likely to encounter vehicles at intersections, driveways and alleys more often than on a protected lane enclosed within a bridge or greenway,” said Jessica Cicchino, IIHS Vice President for Research and the lead author of the new paper.

“Pedestrians also sometimes enter street-level bike lanes, which can cause cyclists to swerve and fall.”

Protected bike lanes raised from the roadway are the safest, according to the report.

IIHS collaborated with George Washington University, Oregon Health and Science University and New York University on the study which involved interviewed 604 adult cyclists who visited emergency rooms in the District of Columbia, New York City and Portland, Oregon, after crashing or falling.

The paper’s authors suggest cities locate protected bike lanes where there are fewer junctions or consider raised cycle crossings, which have been found to improve safety on protected bike lanes in Europe. They also suggest cities take measures to prevent pedestrians from entering bike lanes.