Position
No increase in travel time
An intervention that lengthens anyone's journey is not carried out. The study demonstrates it beforehand.
The rule
No intervention on the road network may increase journey times. Not an average that improves while someone gets worse: no increase, for any of the relations concerned, in neither the median nor the 95th percentile, at peak or off-peak.
The study comes first
The condition for intervening is a prior study that demonstrates the rule. The study rests on real data from the existing situation, on a network model calibrated on that data and on the simulation of the design scenario. If the study does not demonstrate the absence of increases, the intervention is not carried out: nothing is tried to see how it goes.
Measurement afterwards verifies
After the intervention the same indicators are measured. The measurement does not justify an intervention already made and is not an experiment: it verifies that the study was right. If journey times turn out worse than at the start, the study was wrong, and the intervention is corrected or the previous state restored. The gap between forecast and measurement is published.
What counts as an increase
- a route that becomes longer or slower for those who use it, even in a single time band;
- a wait that grows, at junctions, level crossings, signals;
- a less predictable time: a 95th percentile that worsens even if the median stays the same;
- a deterioration for surface public transport, emergency vehicles or logistics.
To whom it applies
To every category of user of the axis and of the surrounding network: those who drive, those who travel by bus, those who deliver, those who must reach a hospital. The advantage of one category does not offset the increase for another.
The method for the prior study and for the verification is described on the Method page.