Corby Study Assessment
A summary of the following is available on the Corby Study page.
This case study of the application of PRT to a “New Town”, where it would connect extensive new “greenfield” development with the town centre, was made as part of a project for the DfT, but with interest and support from Corby Council and the Catalyst Corby Urban Regeneration Company. However, it also offered a valuable opportunity to compare PRT with LRT, because Colin Buchanan and Partners (CBP) had recently made a feasibility study for LRT (ie a “supertram”) linking the town centre with the new development areas. CBP were particularly helpful in providing the data on which their feasibility study was based, and the mathematical model they used to predict demand.
Figure 1: The proposed Corby PRT (ULTra) and LRT routes. The ULTra network provides easily accessible service to a much broader area.
The Network
CBP identified an alignment and described an LRT system consisting of two lines, with Line 1 running from an area designated for new development to the southwest, through the town centre and via an industrial zone into an area planned for substantial new growth in the northeast. Line 2, which would not be opened until 2016 when new development was beginning in the areas served, runs east from the town centre through two industrial areas to new developments to the east. The whole system required 14.2 kms of two-way track, and 17 stops. The ULTra network examined uses six large open loops of guideway, occupying the same SW to NE corridor as LRT’s Line 1, and the west-east corridor of Line 2, but servicing a much broader area of access. Both LRT and PRT networks are shown in Figure 1 on the right.
It is obviously straightforward to integrate the infrastructure with new construction in the development areas, but it is also the case that even the older areas of Corby offer adequate space for the ULTra guideway, though there are potential concerns about visual intrusion and vandalism in a few places. The pedestrianised shopping centre is planned for redevelopment and is ideally suited to accommodating PRT at first-floor level, with stations inside the shops. There are 30 kms of ULTra guideway and 31 stations, and overall 44% of the guideway’s length is elevated. The system is designed for construction in two phases, beginning operations in 2008 on the SW to NE network and in 2016 on an additional loop to the east, paralleling CBP’s Line 1 and Line 2.
The dispersal and control of the PRT vehicles is crucial, and the system must have sufficient vehicles to ensure that it can always meet the peak demand at any point on the network. Detailed computer simulation shows that the system will require 365 vehicles initially, rising to 895 at the start of Phase 2 and a maximum of 967 in 2021 when the system would carry over 38,000 passengers per day. The average wait time is only 17 seconds.
Financial and Social Assessment
At the start of operation in 2008, the infrastructure of Phase 1 has 13 kms of guideway at grade and 10 kms elevated, with 25 stations. The capital cost is £68.2M, including vehicles. Operating costs would be £3.3M per year. The vehicle requirement and operating costs increase with demand, until Phase 2 opens in 2016, adding 7.3 kms of track and another 6 stations, plus additional vehicles, to a cost of £25.2M. The combined operating cost of both Phase 1 and Phase 2 is £5.1M, and the total capital costs of the system at 2016 are £97.6M, rather higher than the £93.5M of the LRT system, which is shorter and has fewer stations, but the main difference is due to the large number of PRT vehicles required to carry many more passengers than for LRT. It is also the case that the LRT cost estimates for Corby are substantially lower than the mean of recent LRT systems, as surveyed in EDICT (2004).
The CBP modal split model was applied to the ULTra network using seven fairly coarse zones and the CBP trip matrices. At the start of the 20-year period modelled these zones accounted for 69% of trips in the town, and by 2027, after much new development, for 76% of trips. Although this study uses the CBP model and data, some details of the trips between the seven zones were no longer available and had to be synthesized from the zonal trip totals. The present study showed excellent agreement with the CBP study for patronage and revenues on LRT in 2027, but in earlier years it predicted slightly greater usage of LRT than the CBP study. Consequently, the results are not directly comparable with those of the CBP study. Treatment of ULTra and LRT within this study is exactly comparable, however. It is assumed that ULTra will charge a flat fare of £1.50 per vehicle, because at the assumed average occupancy of 1.33 the mean fare per passenger is £1.13, close to the mean LRT fare of £1.09.
The CBP demand model predicts that ULTra would attract 19.3% of trips made in the seven zones, compared with 11.4% for LRT (when the full systems are operating). In particular, ULTra would capture 17% of existing car driver trips in this area (though only 8% of the mileage) and 37% of car passenger trips, compared with 10% and 21% for LRT. Overall, ULTra would carry 13.0M passengers per year, gaining revenue of £14.7M, compared with 7.7M passengers and £8.4M revenue for LRT.
Summary of costs and benefits of Corby PRT and LRT.
Financial and social assessments of the two transport schemes over 30 years at a 6% discount rate are summarised in Table 2. Both cover their operating costs easily, but LRT revenues are insufficient to cover the capital costs, and the NPV is -£68.6M, while PRT has a positive NPV of £3.5M. However, neither of these analyses makes allowance for vehicle renewal. When this is included for ULTra the NPV falls to -£13.9M. The effect on the LRT assessment is not known. Additionally, though, the ULTra network runs close to areas outside the seven zones served by LRT, and would attract extra demand. The LRT lines are too far from these areas to benefit from additional patronage, but it is estimated that they would increase the start-up demand for ULTra by 27%. This additional demand could be estimated only crudely, but with appropriate adjustments made to the vehicle requirements and operating costs to cover it the 30-year NPV becomes +£3.8M. The network studied here has not been optimised to maximise the financial return: it is very likely that further examination of the trade-offs involved would improve its performance. There is also scope for a higher fare: a £2 flat fare (ie a mean of £1.50 per passenger) gives a 30-year NPV of +£27M.
Social benefits, comprising passenger time and cost savings (halved according to the standard “rule of a half” for modal transfer), accident and energy savings have been calculated in a similar way to those for the Cardiff study. No benefits from reduced congestion are assumed, since traffic congestion causes few problems in Corby. As Table 2 on the right shows, these increase the NPV to £188M, excluding the additional demand from neighbouring zones. ULTra has substantial environmental benefits, and would reduce total emissions by 62 tonnes of carbon monoxide, 5 tonnes of hydrocarbons, 10 tonnes of nitrogen oxides and 1 tonne of particulates per year. It also shows a net saving of 3600 tonnes of the greenhouse gas carbon dioxide per year after allowing for emissions from the generating stations which power ULTra.
