As Easy As Riding A Bike)
…The other interesting detail from this report is… London. This document essentially acknowledges that the National Transport Model has failed to predict that the amount of car traffic in London would fall as much as it has –
… analysis of our forecast from 2003-2010 shows that although the NTM predicts a fall in London car traffic of 1.5%, this was not as great as the actual 7.8% fall in traffic count statistics.
What’s the explanation?
We believe that the reason for this short-term model error and long-run discrepancy with other forecasts is due to:
Car Ownership – the number of cars per person in London has been relatively flat over the last decade. While we have different car ownership saturation levels for different area types, including London, these may need to be re-estimated.
Public Transport – London has seen high levels of investment in public transport, capacity and quality improvement on buses and rail based public transport. London will continue to see high levels of investment in public transport with increase in capacity into the future, e.g. Cross Rail. We will need to revisit our modelling on the impact this may have on car travel.
Road capacity, car parking space cost and availability – There is evidence to suggest that In recent years London road capacity has been significantly reduced due to bus lanes, congestion charge and other road works. There is also a significant constraint and cost to parking in London which would reduce the demand to travel by car. We will need to revisit our modelling on the impact this may have on car travel.
On each of these three factors, the DfT are admitting that their model needs to be ‘revisited’ – their model simply hasn’t correctly taken into account the effect of public transport, and reallocation of road space, on the amount of car traffic that might be on the roads.
It’s also worth noting this ‘London’ example appears to show that levels of car ownership – which the DfT tie closely with GDP per capita – might be much more strongly affected by these other two factors assessed here, public transport and use of road space. Again, a challenge for the DfT modellers.
It seems that the DfT are admitting that their model doesn’t accurately take into account factors beyond income, population and fuel costs, their ‘key drivers’ – which is hugely significant if, as is likely to be the case, urban areas (in particular) in England continue to reallocate road space to other modes of transport, and prioritise these other modes, ahead of car travel.
Certainly, planning for future growth in car travel using a model that the DfT itself admits isn’t properly reflecting other factors on car demand looks increasingly silly.
Responses to The DfT and their car traffic forecasts
- rdrf says:
November 28, 2014 at 6:53 pm
It’s silly to say that :
- “Certainly, planning for future growth in car travel using a model that the DfT itself admits isn’t properly reflecting other factors on car demand looks increasingly silly.”
Because it is not a question of “silly”. Forecasting by the DfT and its antecedents has ALWAYS been about accommodating and colluding with increasing motor vehicle use. Take a look at John Adams work such as “Transport Planning: Vision and Practice” from decades ago, along with his critiques of Cost Benefit Analysis – another numbers trick set up to support more motorisation. Because of this some green academics like John Whitelegg have advocated “backcasting” – wherein you work out what you want in he future and then work out what to do to achieve it. Either way, the thing is to examine the ideological underpinnings.
For example – why should motoring become cheaper ?
Even without other costs going up, shouldn’t motoring have become more expensive?
Shouldn’t traffic law be enforced (which means that a larger number of those not prepared to/able to drive properly wouldn’t be out there in the first place)?
And how about reducing car parking at origins and destinations? Or reallocating road space to more benign modes (which, incidentally, I haven’t noticed happening very much in London).
(my emphasis – SE)