London scoping - ukcip

7.3.6 Road Transport
Final Report
160
Context
The Mayor’s Strategy notes that high car use rates in London currently ensures that the city
experiences high levels of road congestion - and therefore lost time - on a daily basis.
Flooding and Rainfall Intensity Impacts
Climate change impacts on use of road transport are suggested to include travel disruption due
to flooding incidents on vulnerable stretches of road, resulting from high rain intensity events.
Temperature Change Impacts
Buckling of road surfaces may occur in spells of hot weather during summer months. This was
the case of the historical analogue of summer 1995 when asphalt roads were subject to
‘bleeding’ and ‘fatting up’ due to the binder materials melting and resulting in road rutting.
Indeed as a result of this event, the British Standard specification for road surfacing
performance was amended (Palutikof (ed.) 1997). It is not known whether the revised
specification will be adequate for future climate change related hot days.
The 1995 analogue also provides evidence that car use (and indeed rail use) for leisure is
positively related to spells of warmer weather. Participants in the stakeholder workshop also
felt strongly that alternative forms of transport, and particularly bicycle, would have increased
in usage. It was noted at the same time - and in fact is confirmed by the 1995 analogue - that
there might be more bicycle-related accidents as a consequence. This risk is clearly one that
could increase in London if there were better weather. However, it is likely that there would be
an adjustment in the behaviour of both cyclists and motorists over time, which would reduce the
risk (i.e. as drivers became more used to a higher volume of cyclists on the roads, and as cyclists
became more knowledgeable and experienced about the cycling conditions). Much would
depend upon safe design of cycling routes and lanes. More cycling to work would create a
higher demand for showers at work, requiring installation into new buildings at least, and
increasing the water demand of offices.
Stern and Zehavi (1989) conducted research on a road affected by high temperatures (above
24°C) and found that the risk of accidents increased during hotter weather. The research had
been carried out on a desert highway, however, which did not have obstacles such as parked
vehicles and trees, and found that most accidents consisted of cars running off the road or
turning over - a result of heat stress on driver concentration. Thornes (1997) (after Maycock
1995) reports that a survey found that 9% of drivers felt that warm weather induced drowsiness
whilst driving. Hotter weather would not only make the experience of driving a car or other
vehicle in London less pleasant: it might therefore also increase the risk of accidents. At the
same time, the impacts of higher external temperatures would be overcome by the use of AC
within cars. This is an increasingly common feature of new cars, and could be expected to
become a routine accessory in the next decade or so (at least under GM), even though it reduces
fuel efficiency.
A further issue raised by stakeholders as a possibility is that in the event that public transport
improvements do not keep track with climate change (air-conditioning was given as an
example) this might force people to use private cars more often.