in dense traffic, congestion can happen for no obvious reason.
Sometimes, all it takes is slightly erratic driver behavior, like sudden slowing down, for the notorious ‘ripple effect’ to occur. The slower speed creates a sustained traffic jam.
No real alternatives to driving
When people don’t have public transport options in their city (or they’re inadequate), they depend on private vehicles to get around. But surface area is limited for building roads and parking lots.
Road capacities are maxed out