GENEVA, Switzerland — In the wake of a fiery crash killing at least 14 people, European road transport experts are calling for improved tunnel safety smaller fuel tanks for heavy trucks.

The initial investigation indicates the accident was likely caused when a northbound truck shot across the median, colliding head-on with another truck. Both vehicles burst into flames.

There were approximately 100 cars, one tourist bus and about 15 rigs in the tunnel when the accident occurred. Most vehicles were able to back out, including the bus. However, police on the scene say 20 to 40 vehicles were pinned under the rubble in the partially collapsed tunnel.

“The main cause of accidents in tunnels or outside of tunnels is road users’ behavior. The bulk of the measures concern that,” Jose Capel Ferrer, director of the UN Economic Commission for Europe (ECE), tells local media. “It is important to raise awareness of how dangerous it is to drive in a tunnel and how to behave in case of a breakdown or accident in a tunnel.”

He also suggests distances between heavy trucks should be better controlled and truck drivers should be tested every five years. Ferrer adds, “generally you take one test and it is good forever.”