London Bus, England

The Customer

London buses now cover more route miles and carry more passengers than ever before. More than 8000 buses now serve more than 700 routes throughout Greater London, and usage has exceeded six million passenger journeys every weekday. London Bus Services Ltd is a division of Transport for London, and operates one of the largest bus networks in the world.

The Challenge

The company's legacy radio network recently celebrated its tenth anniversary in service. For radio infrastructure, of course, this is no cause for celebration. This is the age at which reliability begins to suffer, and attrition rates rise dramatically. It is also usually difficult to buy identical or compatible replacement units.

This was the problem facing London Bus's Technical Services Group (TSG). The capital and operational costs of moving to an entirely new network would be extremely high. Not only would each bus require a complete radio refi t, but the control centre, located at Trinity Park, would also need to be upgraded with new equipment.

A new system would also have to be comprehensively re-specified internally before tenders could be invited, which represents significant effort on the part of LBSL technical staff. Retraining controllers and drivers to get the best from the new system also represents a high cost to the bus company.

The Solution

TSG specified that the new radios should be directly compatible with the existing interfaces through which the radios are programmed and controlled. TSG's goal was a mobile radio solution capable of plugging in directly wherever an obsolete unit is removed and ready to be used in exactly the same way as its predecessor.

This would represent the most operationally effective, lowest cost, most easily-commissioned solution. After evaluating several responses to the tender, TSG selected the solution proposed by Tait Electronics, based on its analogue mobile radio set. Tait proposed to customise its off-the-shelf radio set to meet the special requirements for bus applications in the same way as the existing radios.

In particular, the tender demanded an identical interface to the buses' ticket machine, which the drivers use to programme the unique route number into the radio each time the vehicle begins work on a new route.

This data is combined with AVL data for control, management and PIBS purposes. The driver must also update the running number and trip numberfor successive trips throughout the shift. Maintaining this interface to the ticket machine is vital if the radio is to respond in the same way to each button push, and thereby save the burden of retraining each driver to use the new radio. Also, the tender required an identical, compatible interface to the on-board AVL modem.

Retaining the existing AVL equipment on board each bus would save change over costs and contribute to a generally smooth upgrade. Tait also recreated the original radio's fall back mode, designed to enable open channel communication in the case of loss of the control channel.

The Outome

After initial trials at one garage, the new radios began rolling out to contracting operators throughout London. This ability to gradually migrate large numbers of units provided to several independent operating companies, without suffering loss of interoperability or incurring retraining costs, has proved vital to continued operation of economic yet modern and fully functioning services during a period of enormous growth and rapid change for
London buses.