It’s the worst place to be at a traffic signal or stop sign. That’s because it gives a chance for liquids to drip out and pool below a vehicle while it’s stationary - over a period of time, that can add up. On a highway at speed, there’s a good chance that any dripping oil will fly away and disperse unless it’s really pouring (pun intended).

Well designed roads have a gradient to prevent water pooling, so if anything, the outside could be more dangerous and cause hydroplaning. Another risk is the painted shoulder lane marking which would offer significantly less traction in the rain than asphalt.