| Topic: | Re:Re:Re:Cars, Cherry Trees, Chiswick and Carbon | |
| Posted by: | Mark Evans | |
| Date/Time: | 24/02/20 15:23:00 |
| Chiswick isn't an economic island, it is an integral part of a large city so you can't plan transport for it in isolation. Closing or restricting through traffic is just going to divert the problem from an A road (the A315) to B roads because at some point in the diversion they will have to be used. The problem with a lot of the proposed solutions is that they ignore the inelasticity of demand for motor vehicle journeys. The DfT figures for the last decade (up to 2018) show that in London both car and over all motor vehicle miles travelled have been within a fairly narrow range. At the same time our roads have become steadily more congested as more capacity has been devoted to buses and bikes. I'm not against this policy as we clearly need to rebalance transport but, at the same time, we shouldn't be ignoring the cost and the fact that if demand is static and capacity is reduced there will be more traffic and more pollution. The idea of traffic evaporation is a nonsense one and demonstrably isn't working in London over the last decade so you can't reduce road use by reducing road capacity. Edward posted an important stat earlier on which showed that 14% of vehicle journeys in London are under 1km. In terms of miles travelled you probably have to at least halve that number so in terms of distance travelled let's say 5% of vehicle journeys are under 1km. These are the journeys that are potentially most substitutable and could be converted into carbon free alternatives but a large proportion of them won't be substitutable for a variety of reasons e.g. someone is doing a big shop, they have mobility issues, they need to transport something more heavy than they can carry. At least half if not the majority of short journeys will be non-substitutable so even if you managed to get all the rest to switch you would only be making a dent in the total overall journey miles in London. We have to accept some hard realities here. Successes in reducing vehicle use in London earlier in the century have stopped working over the last decade and it is going to be very hard to develop policies that bring about further reductions without substantial economic cost, giving road space to alternative means of transport is something that has to be considered but if increased journey times overall are the result then it may not be the answer at a local level, particularly in this part of London we are going to see significant population growth which inevitably will lead to increased demand for road space, that same road space is not growing in fact its capacity is being reduced in certain circumstances. The only practical way to reduce the congestion that will inevitably result is improved mass transit systems but we know for the next decade at least in our neck of the woods that isn't going to happen and with the government's policy of 'levelling up' London's transport infrastructure is going to be starved of capital. In fact what has happened in Chiswick is that there has been a substantial reduction in capacity on the bus network which might have short term benefits in terms of traffic flow and air quality but will have negative consequences longer term as people switch back to cars from buses. We probably just have to accept that until technology kicks in that reduces congestion, rather than increasing it like Waze does, we are entering a period of increased traffic in this part of London and the only policy option that we have that is practical and affordable is planting more trees. |