Two-thirds of car passengers have felt uncomfortable with speed when driven by a friend or family member, according to new research.

The study, commissioned by Transport for London (TfL) and carried out by YouGov, also revealed that almost 30 percent of car passengers would feel uncomfortable asking a friend or family member to slow down.

“It seems that driving at an unsafe speed has now sadly become socially acceptable and many people simply don’t think of it as a risk,” said Stuart Reid, TfL’s Director of the Vision Zero campaign.

“I would urge drivers to slow down and also encourage people who feel uncomfortable with the speed they’re being driven at to speak up.”

Latest statistics show 103 people have died on London’s roads already this year and analysis by TfL of historical casualty figures recorded by the police suggests that speed accounts for 37 percent of all deaths and serious injuries.