Lets redefine the 2% increase car usage by mode. That comes out to a 3.5%-4% increase in traffic at peak times compared to without the RR and without calculating induced demand.
The numbers above would suggest that should be closer to 40%.
The numbers above would suggest that should be closer to 40%.
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This paper shows the relationship between lane miles and vehicle miles travelled. This suggests a 10% increase in the short term leads to just a 0-4% increase in traffic. But long term this goes to 5-10%.
GRR would add about 55km of lanes. So lets say 37%. So long term will traffic actually increase by 19-37%?
They say VDM should be used when:
1️⃣ A scheme significantly alters travel times
2️⃣ The network is already congested
3️⃣ The scheme likely induces new demand
Yet no VDM was used. No elasticity-based trip-generation. Just a “forecast-only” model assuming fixed trip demand.
That’s not enough for a €700m megaproject when we have climate commitments.