Motorway Bus Lanes - a False Dawn or the Start of a Revolution?
WHITE C D, Mort MacDonald, UK 249
The Government's White Paper 'A New Deal for Transport' has signalled a landmark change in the direction of transport policy in the UK. It recoghises that building new road capacity to cater for ever increasing forecast demand for travel by car cannot be
The Government's White Paper 'A New Deal for Transport' has signalled a landmark change in the direction of transport policy in the UK. It recoghises that building new road capacity to cater for ever increasing forecast demand for travel by car cannot be sustained, especially in its impact on the environment. The new approach relies on policies aimed at discouraging car travel and improving public transport as part of an integrated policy. Buses are to play a key role within this new approach and the White Paper states that buses are to 'lead our transport revolution for the 21 st century.'
The future role for buses is set out in the daughter paper 'From Workhorse to Thoroughbred: A Better Role for Bus Travel'. The founctation for the new policies is the development of partnerships between local authorities and bus operators to drive up the quality of service offered to the traveller. Quality Partnerships will see local authorities and bus operators working together to provide higher quality vehicles that are more comfortable, accessible and cleaner; better customer facilities and bus information; ticketing that makes it easier to use a number of different services; and traffic management schemes to help buses avoid congestion and make their journeys more reliable. Where these partnerships have already been tried there have been notable successes in increasing bus ridership against a background of decreasing travel by bus over the years. Statutory powers are proposed to strengthen Quality Partnerships or introduce contracts as currently operated only in London.
For these policies to succeed it will be necessary for all of the elements to be implemented to provide a real improvement to customer service. As congestion has spread out geographically from conurbations and town centres to the road network between these centres, it is necessary to address congestion on these routes to offer a good quality service by bus for many travellers. The motorway network provides the main spine road network between major conurbations and passes around or penetrates major centres. Much of this network suffers from congestion for a number of hours during a typical day, caused in part by many drivers who could alternatively use public transport for say commuting trips. Rail may provide an alternative for many trips but in parts of the country the rail system too is operating at capacity. A more efficient road based alternative (in capacity terms) is to travel by bus or coach, but why would a car driver choose to take a bus if it is subject to the same congestion as the car? The evidence is clearly that most do not.
A key element in attracting travellers to choose bus travel for their journeys is the improvement of journey times and especially the reliability of journey times. Motorway bus lanes can produce substantial reductions in journey times during congested peak periods. For the operator this can potentially offer the opportunity of increasing service frequency using the same fleet and for the traveller it improves confidence in reaching their destination on time and more quickly than by car. Car travel is predicted to increase nationally by between 16% and 33% over the next 15 years. The forecasts for the busy South East region of England are similar and even in outer London car traffic is expected to rise by between 12% and 25%.
However, sections of the motorway network in the South East operate at capacity for a number of hours during typical working days. Traffic congestion reduces travel speeds substantially so that motorway sections of journeys that take 5 minutes in free moving conditions can last up to 30 minutes. These sections of the motorway system cannot achieve any significant increases in throughput at these times. Many drivers respond by altering their departure times. The consequence is peak spreading resulting in heavily congested conditions during possibly two or three hours in each of the morning and evening peak periods, but there must be some limitation on how much drivers can change their travel behaviour in this way.
Whilst measures such as ramp metering are aimed at squeezing even more capacity from the existing system, they can only achieve relatively small scale changes. So how much difference could a bus lane make?
The throughput capacity of a motorway lane is about 2,1.00 vehicles/hour assuming a typical peak hour proportion of heavy goods vehicles of 7%. So the maximum throughput of a motorway with 3 running lanes/direction will be a traffic flow of 6,300 vehicles per hour for each carriageway. Most cars making up the commuting flows have one occupant only. Consequently a motorway operating at capacity may be carrying around 5,000 trips per hour in single occupancy cars during the peak periods.
If we assume that the throughput capacity for buses is about half that for cars (1 bus = 2 passenger car units), then the throughput capacity of a bus lane could be around 1,000 buses per hour. However it would be questionable whether a local road network could feed this number of buses onto a motorway lane and whether the demand would ever exist without an explosion in bus travel. But even if we take a bus lane operating at one tenth of its capacity, that is a flow of 100 buses/hour and assume each carries 20 passengers, this is the equivalent to 2,000 trips/hour or 2,000 single occupancy cars/hour, an increase in motorway throughput of about one third. If we take the capacity figure of 1,000 buses/hour and the same bus occupancy, this equates to increasing motorway capacity by almost fourfold! Whilst this may be considered as completely unrealistic, it does highlight the potential for a bus lane to deliver large increases in capacity.
Association for European Transport