Research pick: A safer streetcar by design - "Improvements of a tram shape for pedestrian protection"

Research in the International Journal of Heavy Vehicle Systems has looked at the design of the front of city trams, also known in North America as streetcars, to see whether changes to their geometry and height might be made to reduce the risk of serious injury or even death to pedestrians following a collision. This safety issue is becoming increasingly important as cities worldwide expand their tram networks in the driver towards cleaner and lower-carbon transport.

Trams are generally seen as a safe and sustainable alternative to private vehicles, their operation within mixed urban traffic means that when collisions do occur, they tend to cause severe or fatal injuries. Yet, unlike cars, trams have no established design standards focused on pedestrian protection.

The research used computer modelling to simulate what happens when a  pedestrians is hit by a moving tram. They found that even relatively small adjustments to the shape of the front of a tram and the clearance height from rail to underside might reduce the number of serious injuries and deaths. In the first instance, changes in geometry could reduce the forces experienced by the pedestrian but also push them sideways out of the path of the tram. Secondly, lowering the clearance to less than 185mm would reduce the risk of a toppled pedestrian being run over by the vehicle.

A finite element method (FEM) was used to divide up the complex structure of the front end of a tram into small, simulated components that could be analysed for their behaviour in a collision. On the converse of this, the model tracked the motion of the human body and the forces on the head, chest, and limbs when someone is hit by a moving tram. In this way, they showed that avoiding convex or concave surfaces, which tend to concentrate force on the body, could reduce the severity of injury. Similarly, having an inclination of more than 15 degrees horizontally across roughly a quarter of the tram’s front width improved the likelihood, by 75 percent, of pushing a pedestrian sideways rather than forward. Vertically, a gentle slope of 5 to 10 degrees balanced lower impact forces to the head and chest and avoids secondary collision with the tram’s windscreen.

The findings regarding tram design could be incorporated into international safety standards. This would save lives but also strengthen public confidence in urban tram systems and so support the broader transition to sustainable city transport.

Zhou, H., Liu, W. and Wang, W. (2025) ‘Improvements of a tram shape for pedestrian protection’, Int. J. Heavy Vehicle Systems, Vol. 32, No. 4, pp.561–573.