Proposal 03
Junction geometry
Redesigning at-grade junctions to raise capacity without widening the carriageway.
The problem
A badly drawn junction chokes the road even when the road is wide: lanes that drop, left turns that block the through flow, crossings in the wrong place.
The intervention
Roundabouts, turbo-roundabouts, dedicated turn lanes, realigned approaches and reorganised pedestrian crossings. These are modest interventions, sometimes achievable with markings and small works.
- Where it works
- High-traffic at-grade junctions with irregular geometry, intersections with many turning accidents.
- What to measure
- Junction capacity, average delay per vehicle, accident rate per movement.
- 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.