The predictions by Jonathan Mabbutt and others are both absolutely certain and utterly apocalyptical."We all know the impact will be huge across Chiswick, Kew and surrounds. Expectations are of back-ups all the way into central London along the A4 corridor.""impending gridlock for all A roads from Mortlake, Sheen, Richmond, Kew in the south through to Hammersmith, Fulham, Barons Court, Earls Court, Kensington, and Shepherds Bush"Indeed, the only way London won't seize up is by opening Grove Park as a diversion for motorway traffic and "potentially turn it into a car park".The predictions are based on the philosophy that every single car journey is essential - the journey can't be shifted to another mode, it can't be delayed or retimed, it can't be aggregated with other journeys, it can't be diverted, substituted or abandoned - it has to happen.Thus, if you close a main road, any traffic that can't go down that road must "flow" through other roads. There is another view which is that if you reduce supply of road space, the result is less traffic - the cost of the congestion or extra journey time suppresses the number of car journeys and/or prompts a modal shift. This alternative prediction would be an initial period of higher congestion on alternative roads, but fewer journeys will take place overall and congestion may increase but not to the extremes of Jonathan's predictions. This debate is a bit like climate change where observations of weather (either very hot or very cold) are extrapolated to prove or disprove climate change. The actual "proof" of climate change or traffic evaporation is based on the analysis of large data sets which feels remote to the "real lived experience" of those who've already made up their minds. The interesting one to watch will be the school run - responsible for over 25% of morning peak traffic - and nearly 50% in some areas. If a school round trip doubles or triples in length, you might see parents walking, cycling or taking public transport more and using the car less.
Ed Saper ● 1506d