Demand Responsive Transport

First principles assessment

Why introduce demand responsive transit?

The dominant settlement form of most Western towns and cities (outside the primary urban centres) tends to have low density land use, and therefore low demand for public transport. This makes traditional public transport offerings difficult and financially unsustainable for operators (Enoch et al 2004), and has contributed to a large reduction in bus use and accompanying increase in car ownership to cater to unsatisfied transport demands. This has led to a vicious cycle of reduction in patronage and increase in car ownership in both urban and rural areas (Mageeann and Nelson, 2003). This vicious cycle has led to the paradox of increased overall mobility but poorer access to facilities for those residents who do not have access to a car (CfIT, 2008).  DRT is principally aimed at providing alternatives to public transport services in such contexts, and in wholly rural areas.

The concept of DRT is not novel having been around since the 1970s. There was a surge of interest (especially in the US) in the 1970s with the earliest form of DRT known as Dial-A-Ride Transit. The important motivating factors for DRT at that time were relieving congestion by attracting drivers from cars, providing alternatives for the transport disadvantaged and complementing the existing scheduled rail and bus systems (Higgins, 1976). However early interest in the US in Dial-A-Ride Transit to alleviate declines in public transport patronage was reduced when Federal Urban Mass Transit Administration funding dried up.  Thus, in these early schemes, there were multiple objectives of congestion relief, improved accessibility and support for specific disadvantaged groups.

The 1990s saw a resurge of interest in DRT due to the passing of the Americans with Disabilities Act (ADA) in 1990, requiring public transit agencies to provide complementary paratransit services for persons who are unable to use fixed-route services in their service area (Lave and Mathias, 2000; Westerlund, 2005; Diana et al 2007). This is in fact known as ADA Paratransit (KFH et al, 2008). In the UK, there has been some progress made at the local authority level to make vehicles and transport more accessible to disabled people following the Disability Discrimination Act (DDA; 1995), and some DRT ring and ride services cater specifically for people who are able to demonstrate need for such services. Other groups often targeted with similar specialist services include the elderly, young people and residents (often low-income) of areas poorly served by public transport.  

DRT has also been applied in an attempt to reduce the problem of rural accessibility. For example, CfIT (2008) recommended that central government should consider funding a large scale demonstration pilot of DRT with the aspiration that DRT “would be part of a coordinated approach to rural transport…..road based public transport  services would be designed to connect with each other and with train services” (CfIT,2008 p21). Likewise, the Irish Rural Link (a non profit national network of organisations and individuals campaigning for sustainable rural development in Ireland) has identified DRT as an instrument for enhancing accessibility and sustainability in rural parts of the Republic (Irish Rural Link, 2008).

Derek Halden Consultancy et al (2006) in their report for the Scottish Government suggest that DRT services may be classified into the following four categories as follows:

• High value to agency services : These are services provided to meet the needs of particular public agencies such as social services (e.g. services in accordance with the ADA)
• High care needs: These are services for e.g. non emergency patient transport and community transport usually restricted to a particular category of travellers e.g. for the elderly
• Premium Value Services: These are services defined by the needs to reduce travel tmes, higher degree of customer care and often door-to-door, examples of these include the Airport Shuttles in the US.
• Best Value Public Transport- Greater flexibility in the provision of public transport can ensure better value where demand is insufficient for fixed route public transport.

In this review we focus principally on the last two objectives.

The Markets for DRT

Following Enoch et al (2004) we can identify two segments of the market for DRT services.  The first is captive users (those who do not have a car available for their journey) and the second group are choice users (those who use DRT even though they have a car available). Attraction of the first group supports the objectives of improved accessibility and social inclusion.  Attraction of the second may in addition contribute to congestion relief and environmental improvement.  Enoch et al (2004) found that:

1. the factor most highly rated by both markets w certainty of arrival time
2. the key distinction between the markets was that choice users prefer taxi like attributes (such as personalised and door-to-door service), while captive users required a basic means of reaching their destinations and carrying on with their activities
3. price was an important variable for captive users but was much less so for choice users
4. choice users found comfort to be an important quality attribute.

Demand impacts

The demand impacts depend on which market segments the DRT caters to. In general, because the objectives are social and more to do with improving accessibility, more trips would be made i.e. more trips are actually made as a result of DRT. A study (Corlink, 2003) published for the Corlink scheme (Cornwall England) mentions that 38% of the journeys made using the Corlink services would not have been made if the service did not exist. This raises two conflicting issues; the need to balance accessibility with the desire to reduce the travel from an environmental perspective. On the other hand, if the DRT scheme is successful in enticing choice users then there could potentially be a reduction in the vehicle flows.

Response	Impact on vehicle kilometres by car	Expected in situations
		Some change in departure time may be required to fit in with DRT service availability, but this is unlikely to have any impacts.
		Routes may be longer and more circuitous, especially for many-to-many services, resulting in more vehicle km than a direct journey, but the fact that journeys are shared between multiple users will mitigate this impact to some extent. I.e., if all users made individual direct journeys the total km travelled would be greater. Where a journey was previously suppressed there will be a net increase in vehicle kilometres. Where a DRT service reduces individual car use vehicle kilometres will decrease.
		Some changes in destination resulting in longer journeys may be required to fit in with the DRT service provided, but this is unlikely to have significant impacts.
		A DRT designed to increase accessibility may increase the number of vehicle trips and therefore kilometres, but a service designed to reduce individual car use would have the opposite impact.
		A service designed to reduce individual car use would result in a positive modal shift. A service designed to increase accessibility is more likely to release suppressed demand, but could result in abstraction from some public transport services.
	-	It is unlikely that a DRT service, even one designed to reduce car use would be sufficient to prompt an individual to sell their car.
	-	DRT services are unlikely to have any impact.

	= Weakest possible response,		= strongest possible positive response
	= Weakest possible negative response,		= strongest possible negative response

= No response

Short and long run demand responses

Response	-	1st year	2-4 years	5 years	10+ years
	-
	-
	Change job location
-	Shop elsewhere
	Compress working week
-	Trip chain
-	Work from home
-	Shop from home
	Ride share
-	Public transport
-	Walk/cycle
	-
	-

	= Weakest possible response,		= strongest possible positive response
	= Weakest possible negative response,		= strongest possible negative response

= No response

Supply impacts

There will be limited effects on the supply of road space. DRT helps to increase the supply of public transport. However, there is a concern that private operators may give up bus services that become financially less sustainable under competition from DRT.

Financing requirements

DRT schemes are generally expensive to operate (Enoch et al, 2004; Laws et al 2008). Some examples of the difference between the subsidy levels required for conventional fixed route services and for DRT services are shown in the table below.

Similar conclusions are reached by Enoch et al (2006) who, in their study of the Wigglybus scheme in Wiltshire UK, point out that the “least well performing conventional bus route still has a per passenger subsidy of around two-thirds that of the Pewsey Vale Wigglybus average despite both having similar passenger loads per vehicle trip.”

The level of subsidy required for DRT tends to be very high for two reasons:

1. The low level of fare charged
2. The high cost per passenger of the scheme.

The generally low level of fares charged is attributable to the historical focus of DRT on social inclusion (Enoch et al, 2004).

High costs per passenger costs may be associated with the Travel Despatch Centre and the hardware and software required.  The need to reduce these costs has led to the concept of a Flexible Mobility Agency (Ambrosini et al, 2004), which acts as a broker for all mobility services which encompass responsibilities for all public transport services and not being limited to DRT.

DRT services are often established through start-up funds, such as the UK Bus Challenge Funds, and European Union schemes which give funding for an initial period for innovative services. However, there are few if any guarantees for follow on funding when the initial pump priming runs out (Brake et al, 2006). This has important implications for financial sustainability and continuity of service as well as the danger of “public disillusionment when a service that has become accepted is withdrawn due to lack of funds” (Brake et al 2006, p 5).

There are also instances of privately run volunteer based DRT services that utilise volunteers’ own vehicles, and operate with manual booking and dispatch systems that run at relatively low cost. However these generally serve niche markets, and continuity of service provision is not assured.

Expected impact on key policy objectives

The main focus of DRT is on provision for journeys that would not have otherwise been made due to accessibility problems. Those making such trips can be considered a captive market.  As noted, only by influencing the non-captive market can significant impacts be achieved on other policy objectives.

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

= No contribution

Expected impact on problems

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

= No contribution

Expected winners and losers

The principal beneficiaries will be those for whom the DRT services are designed.  Should a DRT prove successful, it would improve public transport links and might increase the revenues for existing operators, who might in turn improve existing services.  Conversely, if DRT competes with existing services, or adds to crowding on them, existing public transport users may suffer.

The other potential beneficiaries will be local shops and other facilities to which access is improved.

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

= No contribution

Barriers to implementation