Riding the City
Interstates Cut Cities in Half and Riders Pay the Detour
Urban freeways sever the street grid, concentrating every crossing into a handful of hostile overpasses that determine which bike trips are practical at all.
An urban freeway is a barrier long before it is a route. For anyone not driving on it, its main effect is that most of the streets it crosses no longer go anywhere.
Severance is the technical term for what happened
Building a limited-access highway through a city removes the intersections along its length. A grid that offered a crossing every few hundred feet is reduced to crossings every half mile or more.
Transportation planners describe this as severance, and it applies to walking, cycling, and local driving alike.
The through-traffic capacity gained by the highway is real, but it is paid for by everyone whose trip runs across the corridor rather than along it.
Surviving crossings inherit the worst conditions
Because so few streets still cross, the remaining ones carry concentrated traffic. They usually also carry the ramps, which means merging and diverging vehicles at speed.
Ramp junctions are designed for smooth vehicle movement, so they favor wide radii and free-flowing turns that give drivers little reason to slow or scan.
A rider crossing there deals with several conflict points in quick succession, with limited sight lines under or over a structure.
The detour is invisible on a road map
Two points a quarter mile apart on either side of a corridor can be a mile and a half apart by any usable route.
Because the map shows both points and the highway between them, the penalty is easy to underestimate until it is ridden.
This is why bike network plans in freeway cities often look strange, with routes running parallel for long stretches before turning. They are queuing for a crossing.
Underpasses and overpasses fail in different ways
An underpass is usually short, dark, and prone to collecting water and debris, with limited sight distance at each end.
An overpass is exposed and often long, with a climb that pushes riders to the slowest part of their trip in the least sheltered location.
Both are structures with fixed widths set decades ago, which is why retrofitting a protected crossing there is expensive compared with the same distance on open ground.
The fixes are structural and slow
Cities addressing severance generally add dedicated crossings: a bridge or tunnel serving only walking and cycling, placed where the detour is longest.
A smaller number are removing or capping segments of freeway entirely, which restores the surface grid but requires a scale of investment few corridors receive.
In the meantime the practical response for a rider is to learn which crossings are tolerable, because that set, not the distance, defines what the network really offers.
Questions readers ask
Why do people ride on the road next to a cycle path?
Usually because the path is slower, gives up priority at every side road, or does not go where they are going. Directness is a real requirement, not a preference.
Why does a new cycle route sometimes seem little used?
Often because it does not yet connect to anything at either end. Network value grows as links join up, so early sections can look disappointing until the gaps close.
