New road construction

First principles assessment

Why introduce road construction?

Road construction is perhaps most prominently promoted as a means of bringing economic benefits or encouraging economic development. The intention can be that economic benefits would flow from the road’s use in unlocking new areas of land for development, or by reducing distance travelled between places or by enabling time saving for road users by reducing congestion (see for instance, SACTRA 1999; Eddington 2006; Bulkwalter 2013).  However there is significant uncertainty and debate about the relationship between road construction and economic development, and about the way in which economic impacts are appropriately measured. 

• An aim of supporting economic development by reducing congestion through increasing road space risks failure if traffic volumes are expected to rise over time (Eddington 2006).  The risk can be exacerbated if the increased road space acts to induce additional traffic (e.g.  Cervero 2003). This risk prompted the Eddington Study to argue that road construction would need to be carried out in conjunction with demand management, particularly road user charging, if any benefits in reducing congestion were to be realised.
• Assessment of economic impacts of road construction should take account of impacts beyond those associated with time savings from reduction in congestion. External economic impacts (e.g. economic impacts of pollution, collisions) should be considered and this can outweigh economic impacts of time savings (SACTRA 1999, see also Stern 2007).
• The association of economic benefit with time saving is contested (SACTRA 1999; Banister 2008).

Economic considerations might appear to dominate motivations for road construction, but they are not the alone. Some road construction is designed to remove traffic from areas where it is especially problematic, such as residential areas, town centres, historic sites. The intention can be to improve local air quality and noise pollution in areas of habitation; to improve safety; to reduce severance; or to enhance liveability. These benefits may need to be offset against travel time increases if bypasses involve significant diversions. Questions of whether such roads achieve their goals can depend on factors including design, whether there are increases in overall traffic which overwhelm reductions due to the diverted traffic, whether road construction is accompanied by complementary measures, such as road user charging, improvements to infrastructure for pedestrians and cyclists, other accident remedial measures (e.g. speed limits and traffic calming).      

Road construction brings a range of potential difficulties, from the construction itself and land taken for the road, to the impacts of traffic that comes to use the road:

• Land use for road construction can be at the expense of homes, businesses, public space and natural habitat.  
• Resources used for road construction have environmental costs (e.g. Seo and Kim 2013).
• If new roads allow for accommodation of higher overall volumes of motor traffic, this will increase carbon emissions.
• New roads can expose adjacent communities to increased transport related pollution, and associated increases in mortality from cardiovascular illness and cancer (WHO 2013; Loomis et al. 2013). However it should be noted that construction of bypasses can shift some transport related pollution from residential areas.
• Severance: depending on their location and design, roads can act as a barrier for people in communities who need to cross the road to access employment, education, services, and everyday activities (SEU 2003). Roads can also act as a barrier for wildlife, sometimes creating pressure on viability of animal population, dissecting habitat and causing substantial mortality (Marcantonio et al. 2013). 

Demand impacts

Response	Reduction in road traffic	Expected in situations
	/	If road construction increases efficiency by reducing peak journey times, some traffic might return the peak periods.
	/	If road construction takes traffic away from residential or other sensitive areas there might be some benefit. However these can be offset by induced increases in traffic.
	/	New roads might unlock development land. Bypasses might be associated with loss of trade as potential customers no longer drive through a town.
		New roads can induce traffic.
	/	Bypasses might contribute to improving conditions for pedestrians and cyclists in the area bypassed. However increasing road capacity will be likely to prompt a shift to motor travel.
		Increasing road capacity will be unlikely to prompt a shift from motor travel.
		Road construction might contribute to urban sprawl and increase car dependency.

	= Weakest possible positive contribution,		= strongest possible positive contribution
	= Weakest possible negative contribution		= strongest possible negative contribution

= No contribution

Short and long run demand responses

Response		1st year	2-4 years	5 years	10+ years
	Some traffic may return to peak periods in the short term	/	/
	If road construction takes traffic away from residential or other sensitive areas there might be some benefit. However these can be offset by induced increases in traffic.	/	/
	Dis-benefits to bypassed areas might increase over time	/	/	/	/
	If traffic expected to increase over time
	If traffic expected to increase over time	-	-	-	-
	Little longer term impact expected
	Likely to be lagged response

	= Weakest possible positive contribution,		= strongest possible positive contribution
	= Weakest possible negative contribution		= strongest possible negative contribution

= No contribution

Supply impacts

Increased road space directly adds to supply and might act to induce additional motor traffic (e.g. Cervero 2003). There may be reduction in congestion, although the extent of this will depend on whether traffic increases either because of the road construction or for other reasons.  Bypasses which shift traffic from certain areas might contribute to supporting improved conditions for pedestrians and cyclists in those areas, but supply will still be increased unless the bypassed road is closed.  

Financing requirements

Road construction requires substantial capital investment either directly from taxation, or borrowed with interest from the private sector, or in cases such as toll roads, directly from the private sector with people paying to use the road. 

Expected impact on key policy objectives

Objective	Scale of contribution	Comment
	/	Road building may relieve congestion in the short term, but can induce traffic and undermine these benefits.
	/	Some new roads may remove some traffic from residential areas and so improve safety and the quality of local streets.  especially for those living along or near the route, but also if induced traffic impacts on other parts of the road network.
	/	Increased traffic can increase carbon emissions and other pollution. Land use for roads can damage built and natural environment, impose mortality on wildlife if habitats are severed, and construction has associated environmental costs. Conversely, bypasses can improve the environment on bypassed roads.
		New roads risk exacerbating inequalities in safety and accessibility faced by vulnerable road users. Conversely, bypasses can improve conditions if roads in deprived areas are bypassed.
	/	New roads will typically be designed to a higher standard and hence be safer.  Bypasses can remove traffic from accident blackspots.  These effects may to some extent be offset by growth in traffic. If congestion is reduced on parts of the road network (including the new road), and speed increases accordingly then this will bring further risks especially to vulnerable road users.
	/	The relationship between transport and economic development is uncertain.  Roads which access new developments can support the economy.  Those which add capacity may support the economy in the short term, but this can be offset by growth in traffic.  Bypasses may have an adverse effect on trade in bypassed areas.
		High capital expenditure is required. Benefits can be uncertain – see sections above.

	= Weakest possible positive contribution,		= strongest possible positive contribution
	= Weakest possible negative contribution		= strongest possible negative contribution

= No contribution

Expected impact on problems

Problem	Scale of contribution	Comment
Congestion		Road building may relieve congestion in the short term, but can induce traffic and undermine these benefits.
Community impacts	/	Some new roads may remove some traffic from residential areas and so improve safety, air quality and noise.
Environmental damage		Increased traffic can increase carbon emissions and other pollution. Land use for roads can damage built and natural environment, impose mortality on wildlife if habitats are severed, and construction has associated environmental costs. Conversely, bypasses can improve the environment on bypassed roads.
Poor accessibility	/	Some new roads might improve accessibility, either by unlocking areas of land or shifting traffic from congested areas. However new roads can increase severance for vulnerable road users and residents.
Social and geographical disadvantage	/	Some new roads may remove some traffic from residential areas and so improve safety, air quality and noise. New roads, particularly if they induce traffic can worsen pollution, safety, severance and noise.
Accidents	/	New roads will typically be designed to a higher standard and hence be safer.  Bypasses can remove traffic from accident blackspots.  These effects may to some extent be offset by growth in traffic. New roads, particularly if they induce traffic on parts of the road network, can be detrimental to safety. If congestion is reduced on parts of the road network (including the new road), and speed increases accordingly then this will bring further risks to cyclists.
Poor economic growth	/	The relationship between transport and economic development is uncertain.  Roads which access new developments can support the economy.  Those which add capacity may support the economy in the short term, but this can be offset by growth in traffic.  Bypasses may have an adverse effect on trade in bypassed areas.

	= Weakest possible positive contribution,		= strongest possible positive contribution
	= Weakest possible negative contribution		= strongest possible negative contribution

= No contribution

Expected winners and losers

Group	Winners / losers	Comment
Large scale freight and commercial traffic	/	Will benefit as long as increases in traffic do not offset reductions in congestion. May benefit from unlocking areas for development
Small businesses	/	Will benefit if increases in traffic do not offset reductions in  congestion. May benefit from unlocking areas for development. May lose passing trade if traffic bypasses business areas.
High income car-users	/	Will benefit if increases in traffic do not offset reductions in congestion.
Low income car-users with poor access to public transport	/	Will benefit if increases in traffic do not offset reductions in congestion.
All existing public transport users		New roads might encourage shift to motor traffic and reduce viability of some public transport (see Highways Agency 2009)
People living adjacent to the area targeted	/	Increased traffic can create problems if it goes through adjacent areas (see e.g. Highways Agency 2009b). Areas might gain some benefits in air quality, safety and accessibility if traffic is removed from an area. However business may also lose passing trade
Cyclists including children	/	Some new roads may remove some traffic from residential areas and so improve safety for vulnerable road users. New roads, particularly if they induce traffic on parts of the road network, can be detrimental to safety and accessibility. If congestion is reduced on parts of the road network (including the new road), and speed increases accordingly then this will bring further risks to cyclists.
People at higher risk of health problems exacerbated by poor air quality	/	Some new roads may remove some traffic from residential areas and so improve air quality. New roads, particularly if they induce traffic can worsen pollution especially for those who live or work in the vincinty of increased traffic.
People making high value, important journeys		Will benefit if increases in traffic do not offset reductions in congestion.
The average car user		Will benefit if increases in traffic do not offset reductions in congestion.

	= weakest possible benefit,		= strongest benefit
	= weakest possible disbenefet,		= strongest possible disbenefit

= neither wins nor loses

Barriers to Implementation

Barrier	Scale	Comment
Legal		Legislation is usually required to permit the imposition of a contribution, and may limit the scope for such contributions.
Finance		Collecting a contribution will involve cost.
Governance		If cities consider themselves to be in competition, this may result in sub-optimal outcomes. Cooperation between cities would require negotiation.
Political acceptability		There can be perceptions that a levy will reduce competitiveness of an area.
Public and stakeholder acceptability	/	There can be perceptions that a levy will reduce competitiveness of an area. There may also be a fear that contributions from developers will lead to prioritisation for development offering income even if it involves social or environmental dis-benefit. Conversely the public might consider a contribution from developers to be fair if it meets the cost of providing for access.
Technical feasibility		None.

= minimal barrier,

= most significant barrier