The evidence on performance of CTPs is sketchy as there is a serious lack of monitoring. Despite an obvious role for data demonstrating the success (or otherwise) of a plan in securing continued resourcing, only a minority of organisations collect after data. Thus, there are more descriptions of what constitutes a plan to be found in the literature than actual results. The level of detail disseminated by organisations also varies considerably. Some organisations are very open about the details and costs of their plans, whilst others regard such detail as confidential business information. Thus, the first case study is given in detail to provide a comprehensive illustration of a CTP, whilst others are summaries.

Pfizer

Context

Pfizer is "the largest pharmaceutical healthcare company in the world" (Elliot & Chadwick, 2002). The main UK site is just south of Sandwich in rural East Kent, South East England. 6,500 people are employed at the Sandwich site - twice the population of Sandwich itself! Developments at Sandwich over recent years were only granted planning permission on the basis that a travel plan be developed. Further to this, controls on parking spaces were introduced and a second site entrance was required, plus a reduction of the on site car: people ratio of 15%. Additionally, a new UK head office employing 500 people has been opened in Walton Oaks near Reigate, Surrey in Southern England. The site is a brown field site within the green belt around a dense urban area and was granted permission with "an exceptionally strict Section 106 Planning Agreement" (Elliot & Chadwick, 2002). (A Section 106 is the mechanism through which conditions are attached to planning permission granted by the local authority in the UK. i.e. permission is granted on the basis that the developer provides x. x being the development of a CTP or the provision of a bus service for example.) The Section 106 agreement with the local authority entered into by Pfizer in relation to the Walton Oaks site includes:

• Parking cash-out staff incentive of £1,000 per space per annum,
  
• Provision of £100,000 over five years for improved public bus services,
  
• Very limited parking spaces - including those for visitors, spaces were rationed to 300 for 500 staff in the first development phase and 475 for 900 staff in the second.
  (Elliot & Chadwick, 2002)

Not surprisingly, Pfizer describe their CTPs in the UK as "driven by the company's wish to be a good neighbour, for sound business reasons including its business growth and planning requirements" (Elliot & Chadwick, 2002). Pfizer see reducing car dependency as good for the environment, good for employees health and good commercial sense in terms of minimising company costs (especially if road pricing and/or workplace parking levies are introduced in the future). The current congestion causes expensive delays to commercial traffic as well as employees, whilst devoting space to parking is a waste of valuable development land. A new parking space costs £2000-£3000 ($2,912-$4,368) in construction of the space, access roads, lighting etc, and has an annual running cost, including amortisation, of £400-£500 ($582-$728 at 2002 prices), excluding land costs (Elliot & Chadwick, 2002).

The CTP has seven elements:

• Parking cash-out
  
• Staged improvements to public transport including trains and shuttle buses
  
• Cycle/Motorcycle provision
  
• Ride sharing
  
• Infrastructure improvements
  
• Better site access and on site networks
  
• General enablers and publicity

The parking cash-out is a £2 ($3 at 2002 prices) credit per day to drivers at the Sandwich site who leave their cars at home. The value at the Walton Oaks site is £5 ($7 at 2002 prices) per day. The cash-out is designed to level the playing field, in as much as drivers receive a hidden subsidy equal to the value of maintaining a car parking space, which those who do not drive cannot benefit from. The credit is administered through smart site access cards which are used to access car parks as well as buildings. The credit initially takes the form of points, which are converted to cash received through the pay packet. The cash-out in Sandwich is complemented by the local authority introducing controlled parking in the town six months prior to the credit being introduced, thus reducing the potential for employees to park off-site and collect the cash-out. Whilst £2 may not be enough to encourage staff to seriously consider alternative travel arrangements, it should not cause them to search too hard for spaces outside the site either, or encourage other operators with spare land to open car parks near by. The higher cash-out at Walton Oaks may cause some problem, but "a Traffic Trust fund has been set up to tackle traffic or parking problems when and if they occur in the immediate vicinity" (Elliot & Chadwick, 2002). Administering this system through the site access cards also automatically monitors the key performance statistic - the car: people ratio.

The staged improvements in public transport consist of contract buses (company provided contract buses are tax free) serving local towns and intermediate destinations. These services were complemented by existing local services, although some of these were withdrawn by the local operator and have now been replaced by contract services. The services on contract and existing local services provided a bus at least every half an hour and late running into the evening. These features provide a service for those whose hours are not nine to five, due to shift patterns, off site working or delays to the end of the working day. Times were also adjusted to co-ordinate with local rail services. The existing local services were improved through pump priming payments from Pfizer to the local operator. For contract services, the contract with the local operator includes incentives to improve quality and attract passengers, as well as penalties when agreed targets, such as clean vehicles, are not met. The contract includes obligations and penalties for the operator and Pfizer. The revenue is shared, with the proportions varying if a bus is late, misses a passenger, is dirty or the driver is discourteous. The fares were set to match as closely as possible the petrol costs of car travel.

The nearest train station in Sandwich is over a one and a half kilometres from the Sandwich site, thus improvements to rail services have not been considered so far. However, an existing on demand shuttle service to an outpost office 100 yards from the train station was improved to provide a 10 minute interval service to the office, train station and Sandwich town centre. Special fares have now been negotiated with the local train operator. These are slightly more than equivalent bus fares, but provide for a wider range of destinations/origins and links with contract and other local bus services. A similar shuttle service is provided at the Walton Oaks site, plus a coach service between East Kent and Walton Oaks with park and ride points en route for those living between the two sites. However, the Walton Oaks shuttle services and the coach are severely affected by congestion. As public transport is central to the CTPs, bus priority on main roads and local areas is seen as imperative to plan success. To this end, Pfizer have been lobbying the relevant local authorities in Kent with some success.

Cycle and motorcycle provision includes changing rooms, lockers and showers. These are incorporated into new buildings as well as being added to existing buildings where feasible and economical. On site cycle routes and pool cycles for intra-site movements also form part of the provision. Cycle sheds are also being built or up-graded. Pfizer also work with local authorities, a national cycle campaign group and others to provide safe cycle routes to work.

There is also a motorcyclists user group and loans for motorcycle training. This may be more attractive to those working at Walton Oaks as the geography is unsuitable for cycling. Pfizer provide relocation assistance for those transferring from Sandwich to Walton Oaks.

Ride sharing accounted for an unusually high proportion (18%) of work journeys to the Sandwich site prior to the CTP due to the workforce being concentrated in small towns around the site. The parking cash-out provides a further incentive, but clearly it is not as great as that received by those who do not travel by car at all. A map based computer matching system has been developed and can be used for last minute searches. At Walton Oaks, Pfizer are working with other employers in the area and the local authorities to develop a district wide ride share scheme.

Infrastructure improvements consist of a package of road and public transport improvements referred to as the "East Kent Access Scheme." This is part of Kent County Council's Local Transport Plan (LTP). (LTPs are the five year transport plans required of local authorities responsible for transport provision by the UK government.) The reasoning behind the scheme is industrial regeneration of the area and to ensure that existing jobs are retained. As part of this, the measures are needed to tackle serious congestion in the area (the main access road from the north of the Sandwich site is grid locked daily), which will grow as the Pfizer workforce grows and the local area is regenerated.

It is essential that the scheme is designed to give positive advantage to buses and high occupancy cars. Hence, high occupancy vehicle lanes running to and from the Pfizer site are being designed into the scheme. Similar developments are planned around the Walton Oaks site.

Better site access and on-site routes are provided through the bus and cycle lanes referred to above. In addition, on-site bus routes, as well as the cycle routes facilitate door-to-door travel as much as possible.

General enablers and publicity are the activities undertaken to communicate the need to reduce car use, negotiate appropriate measures for the CTP and persuade people to reduce their car use through incentives and culture change. These enablers include a company car opt out scheme and alterations to the car use policy, senior management leading by example, good information on alternatives to solo driving through a company intranet, briefing sessions and monitoring of targets to chase.

Impacts on demand

The demand impacts resulting from the Pfizer CTP at their Sandwich site are measured in terms of modal shift.

Mode	1998 (%)	2001 (%)
	66.7	58.8
	17.7	20.4
	6.7	11.8
	5.7	5.2
	1.5	1.4
	1.6	2.0
	0	0.3
	0.1	0.1

This represents a more than 75% increase in the market share of public transport amongst Pfizer employees and an increase in ride sharing above the already high levels. The increase in train use appears small but is in fact an increase from two people before the shuttle buses linking the site and the train station were introduced to 20 people afterwards. The shuttle buses transport 150-200 people to and from home daily, and 62% of these say they would otherwise travel by car. In total the shuttle buses carry 500 people per day, up from 60 prior to expansion of the service. It is also note worthy that some regular users have sold second household cars. Cycling appears to have decreased slightly, but it is thought that cycling is very reliant on good weather and the survey was under taken immediately after a particularly rainy period. Walking is unlikely to increase substantially due to the distance between the site and near by towns. The key car: people ratio has decreased from 75:100 to 68:100 - a 9% reduction.

The car: people ratio at the Walton Oaks site is currently 66:100, which is considered particularly good for a site located in an area accessible by road from a large proportion of Southern England. As the site only opened in December 2001, the CTP has not been running long enough to have significant impacts, although staff transferring from Sandwich may have been influenced by activity there. The low ratio is credited to higher than expected use of bus services to the Walton Oaks site, as "staff have made real efforts to locate close to the site" (Elliot & Chadwick, 2002).

N.B. All facts and figures describing the Pfizer CTP under context and demand impacts are taken from Elliot & Chadwick, 2002.

Impacts on supply

The supply of road space has not changed as a result of the CTPs, although future plans in terms of access roads and high occupancy vehicle lanes is likely to change the nature of supply. The supply of safe cycling routes has increased, as have the supply of public transport (bus and shuttle) services.

Contribution to objectives

The objective behind the Pfizer CTPs is essentially to improve company efficiency to minimise costs and maximise profits. The reduction of congestion surrounding sites, better land use and employee health are all elements of improved efficiency. In as much as the CTP at Sandwich has reduced solo driving it will have contributed positively towards all these issues and ultimately company efficiency.

Contribution to objectives below is completed on the basis of contribution to transport policy objectives.

Manchester Airport

Context
Manchester Airport is the main international airport in Northern England, with projected growth to 30,000 staff by 2010 (Manchester Airport PLC, 2002). In 1997 Manchester Airport was granted planning permission to build a second runway. As a condition of the planning permission, the Airport was required to implement a number of strategies to reduce the environmental impacts of the expansion. This resulted in the Green Charter, "a commitment from the Airport to local councils" (Manchester Airport PLC, 1998). The Charter includes commitments to minimise the impacts of ground transport used (by staff and passengers) to access the airport. Consequently a Ground Transport Strategy was launched in October 1997. Targets included in the Ground Transport Strategy are:

• Increase public transport use (by staff and passenger) to 25% by 2005
  
• Reduce staff travelling by car alone to national levels (70%) by 2005
  
• Cap staff car parking spaces to 4,200
  (Manchester Airport PLC, 2002)

The Green Commuter Plan for staff was launched in 1998. Measures initially included in the plan focus on:

• Business travel
  
• Working from home
  
• Bus services, and
  
• Ride sharing
  (Manchester Airport PLC, 2002)

This list now includes:

• All public transport
  
• Improved cycle paths, parking and changing facilities, plus interest-free bicycle loans
  
• Pilot van-sharing schemes
  
• Increased car park charges to on-site employers and relocation of staff parking to the site periphery

Public transport measures have a key role, including major infrastructure provision in partnership with public transport operators, local authorities, on-site companies, Railtrack and the Greater Manchester Passenger Transport Executive. The work started with improvements to the local bus network, including a subsidy for early, late and weekend bus services to make them available to shift workers. After completion of the new Airport Rail Link, the number of services to the station was increased and staff were offered discounted tickets. A ground transport interchange is also due to be opened in 2003 and a Metrolink (light rail) extension is expected to be completed by 2005.

As a result of this work, bus use doubled and cycle use for journeys to work tripled between 1996 and 2000. This reduced the proportion of staff who drove alone from 83% to 63%, against a background of increasing staff numbers (East Midlands Local Government Association, 2001 in Rye, 2002).

N.B. All facts and figures describing the Manchester Airport CTP under context are taken from Manchester Airport PLC website (http://www.manchesterairport.co.uk) unless otherwise indicated.

Impacts on demand
The increasing staff numbers at Manchester Airport clearly result in an increase in demand for ground transport, but the reduction in number of staff driving alone is likely to have resulted in a net reduction in demand for road space. The increased demand for bus services may have increased the number of buses on the road, but this is unlikely to have taken all the space freed by reduced solo driving. However, it should be noted that nothing is known about any possible release of suppressed demand resulting from the availability of freed up road space. The increased rail services and discounted staff ticketing may also have increased demand for rail services.

Impacts on supply
The measures indicated in the ground transport plan material do not indicate a change in the supply of road space, merely a change in the way it is used. The new Airport Rail Link will have increased the supply of heavy rail infrastructure, which will be accompanied by an increase in supply of light rail and interchange infrastructure by 2005. Additionally, the supply of bus services has increased.

The temporary rail link to the second runway construction site was responsible for "removing 186,000 lorry journeys from roads in Cheshire, Derbyshire and Greater Manchester" (Manchester airport PLC, 1998).

Contribution to objectives
The objectives of the Ground Transport Strategy and thus the Green Transport Plan at Manchester Airport are to facilitate growth by improving access to the airport and comply with planning regulations.

Contribution to objectives below is completed on the basis of contribution to transport policy objectives by the overall Ground Transport Strategy.

Stockley Park Business Park

Context
Stockley Park business park is in West London, near to Heathrow Airport. The business park has been built up by the developer, Stockley Park Consortium. Since 1998 Stockley Park Consortium have operated the Stockley Transport Plan. The plan commits the developer to work with employers occupying buildings within the park to reduce car use by 20% over five years. The Consortium work in partnership with the local authority (London Borough of Hillingdon) such that The Plan complements Hillingdon transport policies and accounts for the needs of the local community as well as businesses. As with other CTPs, the plan is driven by a combination of business and planning/development motivations. The key motivations are a desire to improve accessibility, put land to productive use (rather than car parking) and planning requirements (Rye, 2002). The Transport Plan clearly sets the work within the current transport policy and planning context as well as a more local transport context:

"Government Transport Policies, such as the Integrated Transport Policy White Paper, the Road Traffic Reduction Act and PPG13, together with Local Authority Policies, such as Local Agenda 21, … [and Local Transport Plans], influence the transport policies developed by members of the Heathrow Area Transport Forum and Stockley Park" (http://www.stockleypark.co.uk, 2002)

The Heathrow Area Transport Forum is the over arching transport forum for the area, within which the Stockley Park Transport Plan sits. Within The Plan, individual employers devise their own commuter plans (http://www.stockleypark.co.uk, 2002). The Plan began with the circulation of the Transport Plan Consultation Document to site occupiers in 1997. Following this later in 1997, a Sustainable Transport Co-ordinator was appointed and a staff travel survey was circulated.

As a result of the survey, modal targets for the 20% reduction in car use were set as follows:

• 7% from development of the Heathrow North station
  
• 7% from public transport improvements
  
• 5% from ride sharing
  
• 1% from cycling and walking initiatives

These targets result from 60% of survey respondents saying they would consider using public transport if it were improved and existing plans for a Heathrow-St Pancras Rail Station link, plus 30% expressing an interest in ride sharing. The initiatives, which were developed include:

• Funding for existing bus services and improvements to those services
  
• Travel cards and tickets on sale at Stockley Park
  
• Discounted tickets and integrated ticketing system
  
• Funding for feasibility studies to identify future public transport service improvements
  
• Heathrow North Rail Station (although a station may be developed at Hayes instead with public transport links to Stockley Park)
  
• An internet-based ride sharing scheme with free emergency taxi home
  
• An internet-based bicycle user group
  
• A bicycle buddy scheme for inexperienced cyclists
  
• Discounts with local bike shops
  
• Improvements to local cycle facilities
  
• Research viability of east-west cycle route linking Stockley Park to the Borough and London-wide cycle network
  
• Awareness raising communication, including
  
  • Stockley Park on-line community (Spark) including real-time bus information and promotion of alternative travel options
    
  • A travel to Stockley Park leaflet
    
  • Quarterly 'Stockley Travel' newsletter
    
  • National Cycle to Work Day and National Car Free Day events
    
  • Branding of all materials with the 'Stockley Travel' logo
• Measures to reduce car dependency during the day, plus other measures to reduce dependency, including:
  
  • On-line shopping and banking through the 'Spark'
    
  • Promotion of existing on-site services (newsagents, dry cleaners, nursery, hairdressers, currency exchange), mobile library and twice weekly shopper bus through 'Spark'.

As a result of a public transport feasibility (accessibility) study extensions to an existing service and a whole new service were identified as meeting the aspirations of the Stockley Park Transport Plan and the London Borough of Hillingdon with regard to regeneration of the Hayes-West Drayton corridor.

Government policy and possible future fiscal measures are seen as an enforcement mechanism by Stockley Park Consortium, who cannot easily use parking related disincentives to car use, as individual building occupiers control their own parking. However, a number of novel enforcement strategies are being developed, including:

• Commercial mechanisms, such as revising leasing structures
  
• Advising companies to adopt their own enforcement strategies, such as encouraging employees to sell their parking spaces
  
• Development of a car parking management plan in conjunction with the Stockley Park Tenants Representative and individual occupiers, through an audit of car parking provision.

Despite the frequent neglect of monitoring, it is seen as essential and includes four elements:

• Ride sharing patterns [through the website?] to show number of ride sharers, days they share and number of journeys saved
  
• New cyclists through the bicycle user group website
  
• Public transport usage through regular surveys by the operators
  
• Regular travel surveys to monitor change.

The actions and initiatives above have required considerable funding. "Development costs for the Transport Plan to data amount to approximately £150,000" (http://www.stockleypark.co.uk, 2002). Approximately £850,000 has been spent on two local bus services since 1989 and £2.3 million has been pledged for development of the Heathrow North Station, extensions to bus routes and development of new routes, and an east-west cycle route (http://www.stockleypark.co.uk, 2002).

Implementation of The Plan is overseen by the Transport Co-ordinator and the Stockley Travel Working Team comprised of representatives from occupiers, local transport operators and the local authority. The Plan is also endorsed by senior executives of occupying companies, whilst employees are kept up to date through the communication mediums listed above. Additionally, professional advice and support are obtained from consultants and transport associations.

DETR, 2001 in Rye, 2002 lists the following results for the Stockley Park Transport Plan, against a background of increasing staff numbers.

Mode	1997	1999
	88%	84%
	10%	12%
	-	"more than doubled"

N.B. All facts and figures describing the Stockley Park Transport Plan under context are taken from the 'Transport Plan' pages of http://www.stockleypark.co.uk as viewed on the 18/05/02, unless otherwise stated.

Impact on demand
The CTP measures and changes in travel patterns identified above suggest that there has been a decrease in the demand for road travel as a consequence of the CTP, despite increasing employee numbers. The changes in travel patterns also indicate an increase in demand for public transport services and cycling facilities. The public transport split between bus and rail is not known, but the measures and plans outlined above suggest that the increased demand is for bus services and rail infrastructure with accompanying services. Unfortunately, ride sharing figures are not published.

Impact on supply
The information above suggests that there has been no change in the supply of road space, merely the way it is used, but there may have been an increase in the supply of bus services and an increase in rail infrastructure and services is envisaged.

Contribution to objectives

Nottingham City Hospital

Context
Nottingham City Hospital is 5km north of Nottingham city centre. 8000 staff work on site (http://utc.nottscc.gov.uk/index.htm, 2000) and there are approximately 14,000 two-way car trips (including visitors, patients and deliveries) accessing the site each day (Walker, 2000 in Rye, 2002). The hospital is spread across a large site and is currently subject to redevelopment and expansion work. As a result of this expansion and associated planning requirements there is a need to reverse the current increase in car trips to the site.

The CTP was introduced in 1997, commencing with a staff travel plan. The measures introduced as part of the CTP include:

• Improved pedestrian and cycle access to the site, including formalising informal site access points (e.g. gaps in the boundary fence).
  
• Improving cycle parking, showers and lockers.
  
• 12.5% staff discount at a local cycle shop*.
  
• Bicycle User Group introduced, which has been expanded into the Alternative Transport Group*.
  
• Nottingham City Council Midi-bus services running through the hospital site linking local estates and suburbs to the hospital*. These services receive no subsidy from the hospital.
  
• Buses run early in the morning and late at night to allow shift workers to use the buses*.
  
• Improved bus shelters around the site, including seating and comprehensive bus information*.
  
• Transport information on the intra and internet sites
  
• Parking charges between £1 and £2.50 per day, with revenue hypothecated to improving non-car transport links to the hospital. (These charges may increase if a workplace parking levy is introduced in Nottingham*.)
  Source: Walker, 2000 in rye, 2002 except *http://utc.nottscc.gov.uk/index.htm, 2002.

The following results have been achieved by Nottingham City Hospital CTP:

Source: Walker, 2000 in Rye, 2002 except **http://utc.nottscc.gov.uk/index.htm, 2002.
*It is assumed that this is facilitated by the intranet site referred to above
***The main rail station is several kilometres across the city, although there is a local station one and a half kilometres from the hospital site.

http://utc.nottscc.gov.uk/index.htm, 2002 also report a number of other interesting results from the year 2000 staff travel survey:

• 20% of staff live more than 16km from the hospital
  
  • 55% of these drive alone to work
    
• 88% of staff never cycle to work - 22% more than in 1997 - key reasons are:
  
  • 39% no access to a bicycle
    
  • 24% personal safety concerns
    
• 54% of staff never travel to work by public transport - many of those who do [at least occasionally], do so because they have:
  
  • no access to a car, or
    
  • cannot drive

These findings imply that car based commuting is still preferable to many, explaining the substantial increase in ride sharing. Whilst the improvements to bus services have clearly paid off, those living along way from the hospital may live beyond the end of the routes. These distances imply very dispersed journeys, suggesting that expanding the ride share scheme to other local employers, could increase the number of potential matches and up take. The motivations to use public transport suggest that incentives (or further disincentives for car use) could be beneficial. A bus (shuttle) link to the local rail station may also be beneficial, as it was in the Pfizer case reported above. With regard to cycling, the lack of access to a bicycle justification for not cycling despite the discount available at a local store, suggests that other modes remain more attractive. Additionally, http://utc.nottscc.gov.uk/index.htm, 2002 notes that the decrease in cycling is in line with the national average. More incentives to cycle could help, especially if these included safe cycle routes linking local estates and suburbs to the hospital for those whose journeys are short.

Impacts on demand
The results reported above suggest demand for road travel has changed, with a small shift to ride sharing and bus use. This represents modal shift from solo driving and cycling. The increase in demand for bus travel has taken the number travelling by bus above the national average of 8% (http://utc.nottscc.gov.uk/index.htm, 2002).

Impacts on supply
None of the measures reported indicate a change in the supply of road space for any mode. Similarly, the bus related measures suggest that the main change to supply has been an increase in the supply of information and extension to the supply of services through earlier and later running. Possible re-routing to enable services to run through the site may have increased direct supply to the site and decreased supply elsewhere.

Contribution to objectives

Comparison with Experience in the US and the Netherlands
In the US the Federal Clean Air Law made travel plans mandatory for organisations with over 100 staff in major urban areas, during the 1990's. Whilst this law has been repealed as a result of lobbying from the business community, the State of Washington has retained its own law, with the same stipulations. In organisations subject to the law, there was a 5.5% reduction in solo driving from 72% between 1994 and 1999 (Washington State TDM Office, 1999 in Rye, 2002). Approximately "half of the employees in the regulated areas work for …employers …covered by the travel plan law, so it affects …[approximately] 12% of all trips made in the areas, since … [approximately] a quarter of all trips are made to and from work" (Rye, 2002).

This US experience not only highlights the resistance to change from businesses perceiving a threat to their profitability, it also demonstrates the role of legislation and the potential impact if there is a concentration of CTPs within an area. Whilst, US businesses clearly perceived a threat to their profitability, the UK examples cited above suggest that CTPs need not be a threat to profit for very large organisations. Indeed, the motivations to implement travel plans suggest that CTPs are seen as helpful in increasing profits. In some cases this could purely be because physical expansion of operations is not granted planning permission without a CTP and the profits from the expansion are calculated to be sufficiently more than the cost of the CTP. The frequent mention of planning restrictions as a motivation to implement a CTP indicates that there is a role for regulation in increasing the up take of CTPs, however the US experience suggests that blanket legislation is an unacceptably hard stick. In the UK, many local authorities are now able to offer companies support through travel plan officers funded by Central Government. This facility helps to soften the stick that is regulation, by communicating the need for CTPs and advising in the early stages. Communicating the need for change is just as important with businesses as it is with the general public. The potential success of UK planning regulations in instigating CTPs is indicated by the fact that most employers talking to Leeds City Council about CTPs are now doing so because the CTP is required as a condition of planning permission granted. Additionally, there is a continuous stream of companies approaching Leeds City Council, where as a year or so ago, only a few organisations had volunteered and the Council found it necessary to devote resources to recruiting businesses to the idea (Leeds City Council, personal communication, 2002).

Rye, 2002 reports two travel plan reviews carried out in the Netherlands by, Towen (1997) and Ligtermoet (1998). A strong relationship between the measures in a plan and the reduction in drive alone commute trips was identified as follows:

• "About 5-8% for a plan with only basic measures that cost little [e.g. ride sharing];
  
• About 8-10% for a plan with the basic measures and other more expensive measures such as additional bus services to the site and reduced fares;
  
• About 10-15% for a plan with all the above measures, and disincentives to car use, such as car park charging" (Rye, 2002).

These findings are in line with the trends identifiable from the case studies reported above. The case studies suggest that ride sharing is popular (presumably because it does not involve getting out of the car), but that people are prepared to travel by bus when the service is significantly improved. Indeed, improving bus services appears to be central to many UK CTPs run by large organisations. This is likely to be because these organisations have sufficient staff for improvements to services to result in increased patronage large enough to justify the funding and effort, if not make the improvements self-funding. Rail also appears to have a positive role where the link between the station and work place is relatively seamless. (Hewlett Packard in Edinburgh, Scotland reduced their solo commuting by 6%, through a 6% increase in rail travel as a result of a 40% discount for travel to a local station next door to the site (other non-rail measures were also implemented)). However, the more rigid nature of rail travel appears to make bus based measures more appealing as they can get nearer to a door-to-door service.

Gaps and weaknesses
Whilst there are many guides to implementing CTPs available in the UK, there is a lack of evidence on the effects of CTPs. Rye (2002) reports a number of examples with results, which is a significant improvement on previous evidence relating to impacts. Nevertheless, where the CTP covers site visitors such as passengers, patients and their visitors, the available evidence only covers staff travel. Additionally, the majority are large organisations employing thousands of staff.

These organisations clearly have a better ability to absorb the financial and resource costs of a CTP to the extent that they can afford to undertake monitoring, but this does not mean that smaller companies cannot operate a CTP and there is a serious lack of evidence regarding what happens when they do. Where larger organisations have published some data on costs, they may well appear prohibitive to smaller companies as evidence demonstrating the ability of a CTP to be profitable is thin. What evidence there is relies on savings in the cost of parking provision (Ernst and Young, 1996 in Rye, 2002), and it is not clear whether these would be large enough in smaller organisations to outweigh the implementation costs.

Hewlett Packard (cited above) have calculated that their plan cost them no more than £22,000 per year so far, equivalent to £1 per return car trip removed (Rye, 2002). Whilst £1, per return car trip removed may not appear excessive, it is not clear whether similar results can be achieved by smaller companies at similar per trip costs.

Additionally, a 6% reduction in solo car driving will represent considerably more journeys in an organisation with thousands of employees, thus there may be a noticeable reduction in congestion on local access roads, causing noticeable improvements in efficiency. Noticeable impacts may be unlikely for smaller, individual sites, especially those located within urban areas. Thus, there is also a need to obtain more knowledge regarding the impacts of a concentration of CTPs within an area or a CTP covering a number of organisations.

There is also some evidence that non-monetary benefits of travel plans, such as increased staff fitness due to more active travel arrangements and reduced stress due to not spending time in traffic jams are not perceived by employers. Similarly, the monetary benefits such as reduced staff absenteeism and increased productivity are not always perceived (Gladstone, 2001). More work is needed to quantify these benefits.