Position
Flow separation
Wherever possible, flows are separated. Any intervention that overlaps flows that were previously separate must be rejected.
The rule
Traffic flows (vehicles, pedestrians, cyclists, public transport, logistics, emergency services) move better and more safely when they do not overlap. The rule has two parts: wherever possible, flows are separated; any intervention that leads to the overlap of flows that were previously separate is rejected.
Why
Every point where two flows overlap is a point of conflict: it slows, creates waits and accidents, and makes travel time unpredictable. To separate is to remove conflicts, not to move them.
What to separate
- vehicles and pedestrians;
- vehicles and cyclists;
- through traffic and local traffic;
- public transport and private traffic;
- main flows and secondary movements;
- logistics and ordinary circulation.
How to separate
- grade-separated junctions for the dominant flows;
- dedicated, continuous routes for pedestrians and cyclists, physically distinct from the carriageway;
- lanes reserved for public transport;
- service roads parallel to through routes;
- bypasses and ring roads that take through traffic out;
- logistics hubs at the edges and loading bays outside the running lane.
Cycle infrastructure
Cycle infrastructure is admissible only if the route is completely separated: its own right of way, physically distinct from the carriageway and from the footway, continuous along the whole route, junctions included (at different levels, or with dedicated phases that meet no other flow). Even so, a cycle route goes through the prior study and may not lengthen anyone's journey.
What we reject
- Cycle lanes on the carriageway, painted or «protected» by taking carriageway away, and mixed cycle-pedestrian paths: the flows are not separated.
- Shared spaces in which vehicles, pedestrians and cyclists occupy the same carriageway where they were previously separated.
- Closures that dump through traffic onto local streets: they overlap flows that do not meet today.
- Removal of dedicated lanes or rights of way to make room for mixed use.
- New at-grade crossings on axes that are separated at different levels today.
- Mixed bus-bike-car lanes where flows are distinct today.
How it is verified
The prior study includes the map of conflict points before and after the intervention. If the number of points where flows overlap increases, the intervention is not carried out. As with journey times, verification afterwards checks the study.