One problem with a motorcyclist riding directly next to another vehicle is that:

Riding alongside another vehicle is dangerous because the vehicle could veer into your lane and sideswipe you. Additionally, the vehicle could block your escape route if a hazard arises.

• The other vehicle may block the motorcyclist's escape route.
• The motorcyclist can be easily seen by other drivers.
• The motorcyclist may not be able to read signs on the side of the road.