When operating any kind of wheeled vehicle on a bridge deck it is prudent to fit kerbs
These are continuous raised edges to the deck to “train” wheels and prevent them from inadvertently leaving the bridge.
The kerbs will also protect the parapet from damage by the vehicle.
In the image above a particularly wet site required a drainage gap under the kerb and it has been integrated in the parapet. This is only possible in this case because the parapet is made from a very strong hardwood. If it was softwood it might seriously damage the parapet due any impact.