Proposal 04
Bypasses and ring roads
Those with no business in the centre should not have to cross it.
The problem
A significant share of traffic in built-up areas is pure through traffic: vehicles with origin and destination outside the town that cross the centre because no competitive alternative exists. They lose their own time and take away that of those who actually need to reach the centre.
The intervention
Build or complete bypasses and ring roads that are competitive on time, with well-spaced interchanges. A good bypass is also the precondition for credibly reducing internal traffic: first the alternative, then, if needed, the restriction.
- Where it works
- Towns crossed by trunk or provincial roads with heavy through flows, cities with an incomplete ring.
- What to measure
- Share of through traffic before and after, travel time of the alternative compared with the centre, flows on internal streets.
- Guiding rule
- Prior study: no increase in travel time and no overlap of flows. Verification afterwards with the Travel Time Index.
This describes a family of interventions: costs, feasibility and impacts must be assessed case by case with local surveys and a network model.