Memorandum submitted by the Slower Speeds
Initiative
SUMMARY
A systems approach to reducing CO2
emissions from transport indicates that speed control should be
a priority. We discuss the rationale for lowering both the top
70 mph speed limit and the urban 30 mph speed limit in order to
reduce car use, curb emissions and restrain longer journeys.
1. INTRODUCTION
The Slower Speeds Initiative was founded in
March 1998 by the Children's Play Council, CTC, the Environmental
Transport Association, the Pedestrians Association, the Pedestrian
Policy Group, the Road Danger Reduction Forum, RoadPeace, Sustrans
and Transport 2000. We work to raise awareness of the benefits
of lower speeds in controlling the adverse impacts of our transport
system and enabling the use of sustainable transport modes.
The best way to cut CO2 emissions
from road transport is to replace as many fossil fuel powered
journeys as possible by non-fossil fuel modes, reduce total mileage
and increase the fuel efficiency of the remaining mileage by regulating
vehicle design and use.
CO2 emissions from road transport
are increasing with increasing road travel which, in the UK, has
accompanied increasing car ownership. Travelling further because
you can travel faster is an important driver of traffic growth.
Between 1992-94 and 2005 the average distance travelled per person
per year increased by 5%, average trip length increased by 12%
but the time spent travelling has remained about an hour a day
(Department for Transport 2005a).
Traffic on motorways has been growing faster
than on other parts of the network (Department for Transport 2005c)
and this trend is expected to continue (Department for Transport
2003b). This makes motorway speed limits an obvious and urgent
point for intervention.
Increasing average journey lengths increase
both car dependence and CO2 emissions. But cars are
also increasingly displacing the non-fossil fuel modes of walking
and cycling for short journeys.
The acceptance of the dominance of the private
car in transport, with the entire system designed around it, stimulates
traffic growth directly. The accompanying deterioration in conditions
for more sustainable modes, walking and cycling in particular,
also stimulates traffic growth. This pattern of traffic growth
is an example of positive feedback (Clayton and Radcliffe 1997).
Positive feedback amplifies growth, forcing
change in a direction that makes further change more likely. Its
system effects include erosion, overshoot and collapse. Negative
feedback checks and controls growth. Climate change is occuring
as a result of this form of positive feedback in human systems
overwhelming Earth's homeostatic, negative feedback systems of
regulation (Odum, 1975; Lovelock, 1979). Every day there are signs
that we are now approaching, and may even have arrived at, system
overshoot (going beyond a "target value" for the system,
eg the atmospheric concentration of CO2 which would
avoid runaway climate change) and collapse. As the Committee recognise,
forecasts of CO2 emissions by sector show that it is
the transport system that is most out of control and most urgently
needs negative feedback. The question is, are there any effective
and immediate points of control?
Volume, mix of modes and vehicle types and speed
are the three dynamic and interacting characteristics which directly
determine the impacts of our transport system. Recent transport
policy has focused primarily on volume (congestion) and has acknowledged
the relationship between mix and volume with policies to reduce
congestion through modal shift. So far these policies have failed.
The importance of speed control in reducing
the impacts of transport (Plowden and Hillman, 1996) and in influencing
volume and mix has so far not been recognised within government
policy. This is unfortunate because there is an existing regulatory
framework/the system of speed limits/which potentially enables
immediate and comprehensive control of the road transport system
to reduce CO2 emissions.
2. SETTING A
SYSTEM BOUNDARY:
LIMITING TOP
SPEED TO
INCREASE FUEL
EFFICIENCY AND
REDUCE TRAFFIC
GROWTH
CO2 emissions from motor cars are
a function of speed, mileage, vehicle weight, fuel and engine
type, driving style and to an increasing extent optional features
such as air conditioning.
Recent improvements in fuel efficiency have
meant that CO2 emissions from transport have not risen
as quickly as traffic. However efficiency improvements have also
lead to a trend of increasing vehicle weight, size and power.
As a result, the International Energy Agency has warned that "even
a strong uptake of efficient technologies may not significantly
reduce average fuel consumption per kilometre unless these trends
turn around" (International Energy Agency 2004, p 15).
Moreover, fuel efficiency improvements make
travel cheaper, encouraging traffic growth.
Despite improvements in fuel efficiency, the
optimum average speed for all motor vehicles for fuel consumption
and CO2 emissions remains around 50 mph. Bringing interurban
speed limits closer to this optimum would reduce emissions.
It is possible to use official statistics on
vehicle speeds (Department for Transport 2005e), mileage (Department
for Transport 2005d) and fleet composition (Netcen 2003) to estimate
how CO2 emissions would change under different speed
limit regimes (Plowden and Hillman 1996). The Slower Speeds Initiative
has carried out simple calculations for cars and taxis on motorways
using 2003 emissions coefficients from National Atmospheric Emissions
Inventory (Netcen 2003).
19% of Britain's total annual mileage is driven
on motorways, less than 1% of total road length. 75% of the mileage
on motorways is driven by cars and taxis. These vehicles do 18%
of their mileage on motorways. We estimated that they emitted
around 4.08 MtC, or 10% of annual emissions by source from the
road transport sector.
We found that a properly enforced 60 mph limit
would cut CO2 from cars on motorways alone by 0.82
MtC a year, reducing their emissions by 18% and overall emissions
from road transport by 2%. This limited measure would reduce the
recent annual 2MtC increase in UK emissions (European Environment
Agency 2005) by about 40%.
A 60 mph speed limit would deliver within a
year about half the savings expected from the Ten Year Plan by
2010 and 20% to 40% of the savings expected by 2010 from the EC
voluntary agreements with car manufacturers on average fleet efficiency.
In 2004 56% of cars exceeded the motorway speed
limit. Simply enforcing the 70 mph limit would reduce CO2
emissions from cars on motorways by around 0.45MtC a year.
We have developed this work with the UK Energy
Research Centre using more comprehensive modelling with more recent
data to show that the total carbon savings would be far higher.
These results inform a joint submission to the Low Carbon Vehicle
Partnership's Challenge for proposals to accelerate the shift
to low carbon vehicles and help meet climate change targets. The
UKERC/SSI proposal has been accepted as one of the four leading
options and will be published in June.
A lower top speed limit has several advantages
over all other transport policy measures to reduce CO2
emissions. Above all, it is certain/no technological development
or innovation is required. It could be introduced overnight while
other measures remain in the pipeline. A lower motorway limit
would require less behavioural change than other non-technological
measures and would be far less costly than the technological measures
for hybrid engines and biofuels and hydrogen (International Energy
Agency 2005). Reducing average speeds on motorways would significantly
reduce casualties as well.
A lower top speed limit would have three other
very important advantages for damping positive feedback in the
transport system.
Optimising existing capacity
A lower top speed limit would enable much better
use to be made of existing capacity, reducing the demand for traffic-generating
increases in road space. 60 mph is the highest speed for maintaining
maximum motorway capacity. A lower motorway limit would reduce
congestion (Highways Agency 2004). By smoothing traffic flow,
it would reduce CO2 emissions resulting from hard acceleration
and braking. It would also reduce crashes and incidents and the
resulting congestion.
Getting traffic growth under control
By increasing journey times a lower top speed
limit is the only fuel efficiency measure which would help to
restrain rather than stimulate demand for travel, so curbing the
tendency for annual mileage to increase.
We have carried out calculations of the potential
savings if a fixed travel time budget and increased travel times
curbed the distances driven. Using scenarios of moderate or maximum
restraint, we have estimated that a lower top speed limit would
reduce or even reverse traffic growth, further boosting carbon
savings in the transport sector. This step would point the transport
system towards sustainability.
Reducing waste in vehicle design
Modern cars are far more powerful than they
need to be or should be. Most have top speeds far in excess of
the national limit. Lower top speed limits, properly enforced,
would help to reverse the trend to heavier and more powerful cars
by removing their relative utility. Lighter weight construction
would deliver the same safety levels at lower speeds and the demand
for powerful acceleration would be reduced. By limiting vehicle
speed and power through design, the enforcement burden would be
minimised and it would be harder for drivers to develop wasteful
and dangerous driving styles. These changes at the top end would
make cars less damaging, wasteful and intimidating for the short
journeys for which they are most often used.
Enforcement
In the short term enforcement would be by automatic
detection. Time over distance technologies would be the most effective.
In the longer term enforcement would be through adapting the vehicle
to ensure that it underpinned rather than undermined system goals.
Other inter-urban speed limits and CO2
reductions
Reducing the 70 mph limit for motorways and
dual carriageways would have implications for the 60 mph national
speed limit for single carriageway roads. Average speeds on these
roads are below 50 mph, so it is likely that much of the mileage
is being driven much closer to the optimum efficiency. But a lower
limit could help to reduce emissions associated with hard acceleration
and braking by drivers attempting to drive at or above the current
limit. Rationalising speed limits for the whole interurban network
would assist management of the network, including the targeting
of resources for enforcement, engineering and maintenance in order
to control demand and reduce levels and impacts of traffic.
3. RADICALLY
EXPANDING THE
USE OF
NON-FOSSIL
FUEL MODES
FOR SHORTER
JOURNEYS/EQUITABLE
MANAGEMENT OF
THE ROAD
NETWORK IN
BUILT UP
AREAS
In 2004, 39% of all motorised mileage was driven
on urban roads. 22% of all mileage was driven on minor urban roads.
58% of urban mileage is driven on minor roads (Department for
Transport 2005d).
The amount of car use in built up areas, especially
for shorter journeys, makes it an obvious candidate for transfer
to non-fossil fuel modes. Here the role of speed management is
not to set a system boundary but rather to control operating conditions,
to ensure that the road environment is conducive to sustainable
road users. Road safety has an essential role to play in carbon
reduction strategies.
Current travel patterns show the potential for
modal shift
In 2004, 68% of all trips, regardless of mode,
were under five miles. 42% were under two miles and 22% under
one mile (Department for Transport 2005a). Cars are now the most
commonly used mode for all but the very shortest trips. 58% of
car trips are under five miles and 25% are under two miles. 20%
of trips under one mile were made by car in 2004.
These shorter car journeys could be walked or
cycled as current trip lengths show. In 2004 77% of trips under
one mile, 32% of one to two mile trips and 5% of two to five mile
trips were walked. While 54% of bicycle trips are under two miles,
36% of bike trips are between two to five miles. About 34% of
car trips fall within the two to five mile band. This last comparison
shows that the bicycle competes well with the motor car for trips
up to five miles long.
The public are aware that much car use is unnecessary
Numerous surveys demonstrate public understanding
that the car is not always needed for such short journeys. 58%
say that they currently use a car to make journeys within walking
and cycling distance (Department for Transport 2003a). Nearly
40% of people agree that "many of the short journeys I now
make by car I could just as easily walk/cycle if I had a bike"
(Department for Transport 2006). The 1998 Transport White Paper
found that 30% of trips were judged by car users as "hardly
necessary at all" or ones for which a "perfectly good
alternative [was] already available but ignored" (Department
of the Environment, Transport and the Regions 1998, paragraph
2.47).
People may also be prepared to make changes
in their mode choices: over 90% agreed that people should be encouraged
to walk to help their health (97%), help the environment (94%)
and ease congestion (92%) (Department for Transport 2003a).
Walking and cycling are in decline
However, walking and cycling are in continuing
decline in spite of policies to increase the use of these modes.
Between 1990 and 2003 the number trips made on foot fell by 25%
while those made on a bicycle fell by 30% (Department for Transport
2005a). In the late 1990s the UK car mode share was the highest
in Europe while we had the second lowest level of walking per
person in the EU and the sixth lowest level of cycling (Atkins
2001c).
Road danger is a pervasive and serious deterrent
to the use of sustainable modes
The greatest deterrent to the uptake of sustainable
modes is danger. A MORI study for the Commission for Integrated
Transport found 44% of people "said they would cycle more
if the roads were safer and 26% would travel less by car if the
conditions for walking locally were better (Hutton and Klahr 2001).
The DfT research into attitudes to walking and
cycling (Department for Transport 2003a) has found that 37% of
those asked would use car less if there were safer walking routes.
When asked what cycling measures would encourage people to use
their cars less those who cycle most frequently (once a week or
more) score the highest in wanting cycle tracks away from roads
(55%) or more cycle lanes on roads (55%). This indicates that
current road conditions intimidate experienced cyclists. About
half of cyclists use roads without cycle lanes for their trips.
Only one in 10 used mainly on-road cycle lanes or cycle tracks
away from roads. Three quarters of adults agreed with the statement,
"The idea of cycling on busy roads frightens me" and
nearly half (47%) agreed strongly.
A more recent survey by Brake and Green Flag
(2006) reveals that 68% worry about being killed on foot and 36%
of people who never cycle on the roads do so for reasons which
include a fear of traffic.
Road danger was spontaneously mentioned as a
barrier to cycle use in another survey (Department for Transport
2004a). Speed featured in the top eight of unprompted local concerns
in yet another (Department of Transport, Local Government and
the Regions 2001b).
Sustainable road users disproportionately bear
the casualty burden: this demonstrates that safety concerns are
well founded
The road casualty record for built up areas
bears out these concerns. 40% of road deaths, 59% of road deaths
and serious injuries and 68% of all road casualties occur on built-up
roads. Of these pedestrians and cyclists account for 45% of the
deaths, 43% of the deaths and serious injuries and 26% of casualties
of all severities (Department for Transport 2005b).
31% of all road deaths, 50% of road deaths and
serious injuries, and 59% of all road casualties occur on roads
with a 30 mph speed limit. The breakdown for vulnerable road users
is not published but one would expect it to be even higher than
for built-up roads as a whole.
In the UK in 2003, per unit of exposure measured
as distance travelled, pedestrians were 16 times and cyclists
were 20 times more likely to be killed or seriously injured than
car occupants.
These figures do not take into account the problem
of under-reporting and under-recording of casualties, which are
thought to lead to underestimates of serious injuries by a factor
of three for all road users and nearly six for cyclists (Department
of Transport, Local Government and the Regions 2001a; Aeron-Thomas
2000).
Speed is the single most important factor to control
when reducing danger for non-fossil fuel modes
Speed is the most important risk factor in road
safety and in terms of injury severity the next most important
is vulnerability (Elvik et al 2004).
Injury severity is related to impact speed.
At an impact speed of 30 mph the probability that a collision
will be fatal to a pedestrian is about 50% (Elvik et al
2004). The transition from minor to non-minor injuries occurs
at around 20 mph (Elvik et al 2004; Ashton and Mackay 1979).
Reducing travel speed from 30 mph to 20 mph reduces the risk of
killing a pedestrian by about 95%: in addition to reducing injury
severity should a collision occur, the lower speed allows more
time to reduce speed still further (Ashton 2004).
All before and after studies of 20 mph zones
indicate a very large potential for casualty reduction. 20 mph
zones have reduced injury collisions of all severities by 60%
and those involving child deaths and serious injuries by 70% (Webster
and Mackie 1996). A recent study by the Transport Research Laboratory
for Transport for London shows that 20 mph zones reduce all casualties
by 42% and deaths and serious injuries by 53% (Transport for London
2003). 20 mph zones in Hull have reduced the number of people
killed and seriously injured by 90% (Kingston-upon-Hull City Council
2000).
A 20 mph speed limit is a necessary precondition
for the expansion of sustainable modes
"Retrofitting" direct, convenient,
safe, coherent and comfortable networks to enable appropriate
levels of walking and cycling in built-up areas would be expensive,
impractical and probably impossible if it depended on segregated
paths, tracks and lanes to achieve levels of risk acceptable to
the majority of the travelling public. It would take an enormously
long time. It would completely cede the road network to motorised
traffic in urban areas, resulting in . . . positive feedback.
A 20 mph speed limit for most urban roads, on
the other hand, would allow the safe mixing of motorised and non-motorised
modes and would give pedestrians and cyclists the same direct
and safe routes for their journeys as those enjoyed by motorists.
This is approach is increasingly adopted in
European countries where rates of walking and cycling are much
higher and casualty rates for sustainable road users much lower
than in the UK (Atkins 2001c).
". . . the upper speed limit of 30 km/h
[19 mph] is a fundamental condition from the traffic safety point
of view . . . Where the integration of such incompatible travel
modes is aimed for, the 30 km/h speed limit acts as the prerequisite
for avoiding detrimental effects of the speed and mass of motorised
traffic." (Wouters 2001, p 19)
Area-wide 20 mph zones were found to be the
one critical success factor underpinning best practice in the
balanced use of road space in the Commission for Integrated Transport
2001 study of European Best Practice:
"Lower speed limits—blanket 30 kph
speed limits on non-strategic roads were common to all case study
areas and, with effective enforcement, were particularly important
in achieving more conducive conditions for non-motorised travel,
reducing the perceived journey time differential between the car
and other modes, creating safer conditions for pedestrians and
cyclists, and reducing traffic noise." (Atkins 2001c, p 22-23)
To achieve these results between 65-85% of the
network has 30 kph limits. In Munich, with a "pedestrian
friendly city" policy, 80% of the road network has a 30 kph
limit. Some residential areas have even lower limits. Strategic
roads with higher limits (50 kph, or 31 mph) have segregated cycle
tracks. In Graz, Austria, over 80% of the network has 30 kph limits.
Cycle usage increased by 17% while cycling casualties fell. Munich
also has very low casualty rates for vulnerable road users. Graz
and Munich exemplify best practice because they have stabilised
or reduced the use of the car, despite increasing levels of car
ownership. Parking restrictions, high quality public transport
and public relations also play an important part in getting car
use under control (Atkins 2001a).
The use of 30 kph speed limits for roads in
residential, shopping and other "mixed use" areas is
nearly universal in Germany. In Hilden, a town of 50,000 people
near Dusseldorf a 30 kph speed limit was introduced over most
of the road network to improve safety and quality of life and
to avoid the expense of providing a comprehensive network of cycle
lanes. 60% of trips to the town centre are made on foot or by
bicycle (Groll 2005).
Potential reduction of CO2 emissions
In its 2000 review of speed policy the Department
of the Environment, Transport and the Regions argued against a
reduction in urban 30 mph limit on the basis of the potential
increase in CO2 and other emissions, but did not provide
evidence for this position.
The trade offs for CO2 at the urban
level are complicated. It is true that engines of current design
are less efficient at lower speeds. But driving style is responsible
for 10-15% of emissions (Royal Commission on Environmental Pollution
1994). Slower urban speeds would help to smooth traffic, reducing
fuel consumption and pollution. Cold start short journeys are
also excessively polluting but many of these would be eliminated
by the shift to walking and cycling. The arguments for and against
a 20 mph speed limit for the majority of built-up roads have not
been considered in the context of reducing speeds on the interurban
network where the fuel inefficiencies resulting from current speed
choice are very much greater. In the longer term, as explained
above, limiting speed at the upper end would reorientate vehicle
design so that cars would become more fuel efficient at lower
speeds.
Graz's Tempo 30 policy has reduced the wider
environmental impacts of motorised transport. Based on measurements
of their results, it has been estimated that a one third reduction
in the modal share of the car would reduce congestion by 30% and
fuel consumption by 25% (Dekoster and Schollaert 1999).
The CO2 reducing effects could be
much wider if a 20 mph speed limit allowed more efficient land
use. The Urban Task Force recommended that 20 mph should become
"normal" in residential areas and high streets and commended
it as an example of a policy that discriminates in favour of pedestrians,
cyclists and public transport, would attract people back into
urban areas and reduce the need for travel (Urban Task Force 1999).
Enforcement and public support
There would have to be a commitment to securing
compliance with a 20 mph limit through a combination of engineering,
enforcement and public information. But there is already evidence
of public support for a 20 mph urban speed limit. In a British
Social Attitudes survey in 2000 two thirds of people said that
pedestrians and cyclists should be given priority in towns and
cities, even if this makes things difficult for other road users.
80% favoured 20 mph speed limits in residential roads to ensure
this priority (Department of Transport, Local Government and the
Regions 2001b). The 2004 MORI attitudes survey found that "motorists
recognise the need to enforce speed limits, although there are
suggestions that 30 mph is too fast for dense urban areas"
(Department for Transport 2004a, p 6). We assume that the high
stakes and a government information campaign to explain the need
for lower limits would help to justify enforcement but also would
encourage widespread voluntary compliance.
Economic rationale
Spending on road safety, including on 20 mph
limits and zones, is irrationally limited. Road safety interventions
typically achieve a return on investment of 3:1 or higher. Department
for Transport guidance on value for money considers a return of
2:1 or more as "high" and advises that most if not all
schemes with this rate of return, or higher, should be pursued
(Department for Transport 2004b). Schemes with "significant
non-monetised impacts relative to costs can be placed in a higher
category. Because of their very significant non-monetised costs,
it can be argued that road safety schemes with a lower rate of
return, near the Treasury's suggested 1.25 on opportunity costs,
would be justified (Ward et al 2003).
Transport for London have estimated that introducing
20 mph zones on 60% of the borough road network (8,000 km) would
cost £230 million and would save an estimated £313 million
in casualties prevented in the first year, a return of 1.36 (Transport
for London 2003). If engineering works are assumed to have a lifetime
of 15 years and require minimal maintenance, then the return on
investment would be nearer 20:1. The return on Hull's 20 mph schemes
has been estimated at 10:1 (IPPR 2002). Safety cameras have a
benefit to cost ratio of 2.7:1 (Gains et al 2005).
4. COMMITTEE
ISSUES FROM
THIS PERSPECTIVE
Is the DfT's strategy coherent?
The Government lacks a coherent speed policy.
The reason for this may be an unwillingness to accept the need
for constraints on mobility. Promoting mobility while seeking
to reduce the impacts of the transport system maintains positive
feedback. Policies to promote walking and cycling modes that do
not fully accept the need to reduce danger and ensure complete
networks for these modes will not achieve meaningful modal shift
from the car for shorter journeys.
Does the expenditure balance adequately reflect
the challenge?
As we have indicated, road safety expenditure
should be considerably increased. Safety and environmental objectives
are mutually supporting and need to be given very much greater
priority in order to "balance the need to travel." The
current lack of balance significantly exacerbates the problem
of traffic growth and emissions.
What realistically could be achieved by 2010 and
2020?
If introduced immediately, a 60 mph limit on
motorways and dual carriageways would prevent at least four mega-tonnes
of carbon entering the atmosphere by 2010. If lower speeds curbed
or stopped traffic growth the benefit would be much greater. More
detailed calculations to be published in June indicate a much
higher figure for reductions. In the longer term (to 2020) the
carbon reducing effects of lower speed limits would be far-reaching:
reduced annual mileage, reduced motorised travel in built-up areas,
more appropriate vehicle design, more compact land use.
What specific steps should the Department take?
— Reduce the top speed limit to 60
mph maximum, reduce the speed limit for single carriageway roads
to 50 mph maximum, reduce the urban speed limit to 20 mph maximum,
with higher speeds the exception for strategic routes with enough
space to accommodate full width pedestrian and cyclist routes.
— Incorporate national carbon reduction
targets in the forthcoming speed limit setting guidance to local
authorities.
— Treble, at minimum, expenditure on
road safety for high quality traffic calming and street design
and speed limit enforcement.
— Reinstate the national target to
treble cycling by 2010, and commit to an equivalent target for
walking.
— Introduce legislation requiring top
speed limiters for all cars and incentives for the adoption of
variable speed limiters, including Intelligent Speed Adaptation.
Bring forward legislation to outlaw the sale of cars without speed
limiters.
Powering Future Vehicles
The Powering Future Vehicles strategy does not
recognise the effects of vehicle power, speed and intimidation
on modal choice and therefore transport impacts. It concentrates
too much on fuel substitution and fuel efficiency and not enough
on the energy intensity of transport systems which promote hypermobility.
It prioritises very expensive solutions before fully specifying
system parameters and using appropriate system goals to optimise
the behaviour of the system with current vehicles. The existing
fleet would be very much greener if driven more conservatively.
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