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Light rail
SummaryTaxonomy and descriptionFirst principles assesmentEvidence on performancePolicy contributionComplementary instrumentsReferences

A first principles assessment
The effects on supply and demand
Anticipated impacts on policy objectives
Anticipated impacts on problems
Expected winners and losers
Barriers to implementation

Sheffield Supertram pictures

The effects on supply and demand

A new light rail scheme will have both direct impacts as a new mode, and indirect impacts as an alternative to existing modes, particularly the car. Short and long run demand responses indicates the potential magnitude of expected responses.

Response
-
1st year
2-4 years
5 years
10+ years
Change departure time
-
0
0
0
0
Change route
-
2
3
3
3
Change destination Change job location
0
0
0
2
-
Shop elsewhere
2
2
3
3
Reduce number of journeys Compress working week
0
0
0
0
-
Trip chain
2
2
2
2
-
Work from home
0
0
0
0
-
Shop from home
0
0
0
0
Change mode Ride share
0
0
0
0
-
Public transport
4
4
4
4
-
Walk/cycle
0
0
0
0
Sell car
-
0
1
2
2
Change home location
-
0
0
2
2

The primary effect on the supply of transport facilities will be an increase in quantity and quality. The new system will provide extra capacity for public transport as well as impacting on the demand and/or supply of other modes, as shown in impacts on demand and supply of modes.

Impacts on demand and supply of modes

Operating feature

Impacts on public transport

Impacts on car

Impacts on cycling

Impacts on walking

Supply

(Capacity)

LR higher quality than existing public transport, therefore overall quantity (including range of modes) and quality of public transport in an area improved

     
 

Capacity can be increased by adding sections to existing vehicles

Where light rail runs on street, capacity may be taken away from road vehicles; where modal shift occurs from car, road capacity may be freed up, encouraging people who were deterred by congestion to drive (Mogridge, 1997)

   
 

Where road capacity is reduced by on street running, bus supply may be reduced, but significant total increase in transport supply still expected

     
 

Where buses are subject to regulation they may be re-organised to feed light rail, possibly releasing vehicles for use elsewhere

     

Demand

New trip opportunities will be created new trip attractions within a reasonable time will be opened up (limited to corridors where light rail introduced) - higher speed may increase journey lengths and frequencies

Where modal shift occurs, demand may decrease

Where modal shift occurs, demand may decrease

Where modal shift occurs, demand may decrease

 

Departure times unlikely to change significantly unless services operate for longer hours than buses may limit potential increase in demand

     
 

Novelty value may generate trips for their own sake; new system may become a tourist attraction

     

Competition

Where buses are unregulated they may compete with the light rail (e.g. Sheffield initially), leading to excess supply (unlikely to continue in the long term)

      

Segregation

Where light rail is segregated it is unaffected by congestion and is therefore efficient

     
 

Where system is not segregated, light rail can be given priority at signal-controlled junctions, making many journey times faster than by car

     

Frequency

Light rail frequency can be high (safety factors require a minimum headway)

     

Overall, a new light rail system will stimulate demand for travel. Often new light rail lines link outer suburbs with the city centre. This increase in accessibility of outer suburbs can lead to development which may lead to such areas becoming more attractive, drawing new residents who wish to take advantage of the new system to make a fast trip to the city centre. However, such residents are likely to have fairly high incomes and be car owners, so they may make many trips by car, possibly more than they did previously if they have moved from a previous home nearer the city centre. This could lead to more car trips being made from such areas than would otherwise have happened. Such effects will be exacerbated if new residential development takes place near the urban periphery. Even if the new residents use the light rail system for the journey to work, they are likely to use the car for other trip purposes. Thus, a new light rail system could lead to more car trips, but it seems unlikely that such effects would outweigh the direct transfer from car to public transport caused by the opening of the new system. However, it would be very difficult to detect empirically any new car trips resulting from changes in residential locations induced by the new system because of the difficulty in identifying a suitable base against which to compare the new trip pattern.

When a new light rail system is developed, it is common for sophisticated information systems to be provided, typically showing the arrival time of the next three trams at stops and next destination on board the tram. Such information can increase the perceived reliability of the system, making it more attractive to users. If the system is segregated from other traffic, predictions of arrival times are likely to be more accurate than those for buses which can be affected adversely by congestion.

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Anticipated impacts on policy objectives

Objective Scale of contribution Comment
Efficiency 4

By reducing overall disutility of travel

Liveable streets 3

By making streets quieter; allowing development of more attractive urban areas

Protection of the environment 3

By reducing air and noise pollution and pressures on green space and environmentally sensitive sites

Equity and social inclusion 3

By offering a new alternative to the car

Safety 3

By offering a safer alternative to the car

Economic growth 4

By offering a stimulus to economic development; by enhancing the economic potential of existing economic centres

Finance -3

Costs a lot of money

Economic efficiency
A light rail system reduces the average disutility of travel, since only those for whom it offers a lower disutility than their present mode will transfer. Those remaining on existing modes should be no worse off, and if road congestion is reduced due to modal shift from car to light rail, then road speeds should increase, thereby reducing journey-time delay. Because light rail is reliable, (particularly when segregated), it should add to economic efficiency. However, light rail is expensive. Most systems do not cover their operating costs and none cover their capital costs. Hence, they require public expenditure, even when operated by the private sector, as happens in Britain. Spending money on light rail may not be the most cost-effective way to achieve policy objectives such as reducing traffic congestion. More broadly, public money spent on light rail is either public money not spent on health, education or defence, or tax revenue that could otherwise be left for taxpayers to spend as they choose, possibly in ways that create jobs. Such choices are essentially political.
In terms of effects on the property market, developing a new light rail system is likely to increase land values in its vicinity, although possibly not in property which suffers from adverse effects such as noise and visual intrusion. It is likely that there are compensating relative decreases in land values elsewhere, but it is very difficult to detect such effects, because they are likely to be small and diffuse.

Liveable streets and neighbourhoods
Modern light rail vehicles are quiet. They might be regarded as visually intrusive, but tend to be accepted as part of the urban fabric after construction. The intrusion of overhead wires (e.g. Manchester) and support poles (e.g Croydon) can be minimised by careful choice of materials and design. If the system is elevated, then it may be visually very intrusive near to properties, but elevation is unusual because of cost. If a light rail scheme reduces car use, it should make cities more attractive. This is partly through a reduction in pollution from road vehicles. New systems are often linked to city-centre pedestrianisation and other measures to reduce car use, which can make the area much more pleasant, leading to increased economic prosperity, often after initial opposition from local businesses. In residential areas, the light rail layout often leads to pieces of land left unused. These can be turned into linear parks or play areas (e.g. Sheffield). Overall, a new light rail system is likely to make cities more pleasant to live in, partly because of the opportunity for complementary development that it offers.

Protection of the environment
The development of a light rail scheme should lead to less atmospheric pollution in the area and lower consumption of fossil fuels through reduced car use, assuming that road space freed up by initial modal switch is not filled by induced traffic. However, light rail is almost inevitably powered by electricity. Whilst this means no emissions from the vehicle, there are environmental implications in terms of pollution at the power station if fossil fuels are used to generate the electricity. This may also negate reductions in fossil fuel consumption as a result of modal switch. A net reduction in car use will aslo lead to a net reduction in noise. Unless the system is built entirely on the road, there will be land-take. Sensitive landscaping can help ensure that there is not a large loss of visual amenity. It may be possible to increase the protection of environmentally-sensitive sites if the system is segregated, with facilities for animals such as toad crossings being provided.

Equity and social inclusion
Light rail offers the opportunity for those without access to a car to travel quickly and comfortably, improving access to work, health, shopping and leisure facilities. This could include some people with disabilities for whom the low-floor vehicles make journeys that would otherwise be very difficult, possible. However, if a major objective is to reduce car use by offering an attractive alternative, then it has to serve areas of high car ownership, and so is not likely to help increase accessibility for those without access to a car. It is possible that a system built to serve low-income areas, could stimulate the local property market to the extent that low income people sell their properties to those with a higher income seeking good access to the city centre. This may increase equity by transferring money from high-income households to low-income ones, but would probably not increase social inclusion.
As discussed above, light rail is expensive. If its provision is funded from a budget which covers all public transport, then the situation which arose in Los Angeles (Wachs, 1993) where funding from bus services in the inner city serving low-income households was transferred to the light rail system serving high-income households, which could not cover its operating costs, thereby leading to a loss of equity.

Safety
Light rail is safe, both because the technology is intrinsically safe and because operating regimes tend to place heavy emphasis on safety. If there is a net transfer from car to light rail with little induced road traffic as a result of the development of a new system, then it should lead to an increase in safety. In mixed traffic conditions there is potential for accidents with other vehicles and pedestrians, but these can be minimised with appropriate visual and aural warnings.

Contribution to economic growth
One of the commonest reasons for developing light rail is the stimulation of economic development, particularly in the city centre (Mackett and Edwards, 1998). This is particularly true in US cities where there is perceived to be a need to reduce the rate of decentralisation. The logic of light rail focusing on the city centre is that it will attract trips away from suburban centres most easily reached by car, thereby slowing down the net outward drift of activities. If this process occurs, it is unlikely to increase the overall level of economic growth, merely slow down a trend towards what is often regarded as a less desirable spatial development pattern. Retaining economic growth in the city centre may offer economies of scale. However, it could be argued that slowing down decentralisation of activities is interfering in market forces, thereby reducing efficiency and so lowering the overall level of economic prosperity.

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Anticipated impacts on problems

Problem Scale of contribution Comment
Congestion-related delay 3  
Congestion-related unreliability 3  
Community severance 3  
Visual intrusion 2  
Lack of amenity 2  
Global warming 3  
Local air pollution 3  
Noise 3  
Reduction of green space 2  
Damage to environmentally sensitive sites 2  
Poor accessibility for those without a car and those with mobility impairments 3  
Disproportionate disadvantaging of particular social or geographic groups 2  
Number, severity and risk of accidents 2  
Suppression of the potential for economic activity in the area 3  

Congestion-related journey-time delay
By offering an attractive alternative to the car, some motorists should transfer to light rail. This will reduce the number of cars on the road, thereby reducing congestion-related journey-time delay. However, if the release of road space leads to the realisation of suppressed demand for car use, this effect will be negated. It is possible that congestion-related journey-time delay could be increased if very substantial amounts of road space have been transferred from car to light rail and there is no net reduction in car use.
Congestion-related journey-time unreliability
Because the effects on congestion-related journey-time unreliability are through the mode transfer from the car, the effects are the same as for congestion-related journey-time delay.
Community severance

A segregated or elevated light rail system could lead to community severance. However, sensitive design would avoid this problem. Replacement of a road by a light rail system should reduce community severance, but where the two operate together the effect on a particular road is likely to be small, even if the development of light rail leads to a net reduction in car use.
Visual intrusion

Surface light rail vehicles might be regarded as visually intrusive, but are unlikely to be more intrusive than cars and lorries. The overhead wires and supporting poles can cause visual intrusion but careful choice of materials and design can reduce the impact. An elevated system is likely to be visually intrusive, but it would be rather unusual to build an elevated system now. The building of new light rail offers the opportunity to provide visually appealing architectural and landscaping features. In general, new light rail should not add to visual intrusion.
Lack of amenity

A well-designed light rail system with sensitive landscaping should add to amenity.
Global warming

A light rail system will only add to global warming if the method of generation of electricity to power it adds to CO2. If the new system leads to a net reduction in car use, it should lead to a reduction in greenhouse emissions. Overall, there should not be a net addition to the problem of global warming.

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Expected winners and losers

We would not necessarily expect everyone to directly benefit from the introduction of a light rail system. Winners and losers highlights the main groups of people who we would expect to be direct beneficiaries, as well as those who we would expect, in the first instance at least, to lose out. It should be remembered, however, that this only relates to the direct, immediate impacts; mitigating measures could be put in place to help those who lose out. It should also be noted that impacts are focused on the routes served by the light rail system, and that long term impacts as a result of potential changes in surrounding land use and consequently that further a field could be different.

Group
Winners / losers
Comment
Large scale freight and commercial traffic
1
High value journeys because less car traffic, therefore less time spent in congestion the greater the vehicle utilization relatively small proportion of journey distance in urban conditions
Small businesses
3
In areas served by light rail
High income car-users
3
New alternative mode, fewer cars on the road
People with a low income
3 /-3
They will win if they live in an area served by light rail, but they do not and there is less funding for other alternatives to the car, they are likely to loose.
People with poor access to public transport
3/-3
They will win if they live in an area served by light rail, but they do not and there is less funding for other alternatives to the car, they are likely to loose.
All existing public transport users
3
New public transport alternative mainly benefits those living near route
People living adjacent to the area targeted
3
They may benefit from reduced congestion and improved or increased public transport supply.
People making high value, important journeys
3
A new efficient alternative is available
The average car user
3
Where they are able to travel more efficiently, saving time and money.

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Barriers to implementation

As the decision to implement a light rail system can be largely political, there may well be problems associated with this, not least justifying the substantial expenditure. However, further, factors will be the way in which the policy is presented to the public, the public acceptability of the policy and whether the necessary legal powers are in place. The scale of barriers is indicated in scale of barriers.

Barrier Scale Comment
Legal -3  
Finance -4  
Political -3  
Feasibility -3  

These barriers to implementation are likely to be related to the extent to which an area will benefit from light rail, i.e. whether the area is appropriate for such a system. As shown in appropriate area types, some are more suitable than others.

Appropriate area-types
Area type
Suitability
City centre
4
Dense inner suburb
4
Medium density outer suburb
3
Less dense outer suburb
2
District centre
3
Corridor
4
Small town
1
Tourist town
2

 

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Text edited at the Institute for Transport Studies, University of Leeds, Leeds LS2 9JT