The Cambridge busway comes in two parts. One 12-mile section serves 10 stops linking St Ives and Cambridge, and a four-mile section with two stops links the latter to Trumpington. Half-way between rail and road, the busway consists of sunken concrete piles and precast beam sections laid on top. Designed with gentle curves, the busway nevertheless requires buses to be fitted with guide wheels laterally to the near side and
off-side front. Linked to the front steering arm, they – not the driver – steer the bus on the busway sections, until the driver takes over on the portions of the route that run on public road.
As the only traffic is buses, and as each busway has segregated lanes for each direction, it has a higher speed limit than the surrounding local roads; single-decker buses can go up to 56mph, and double-decker, tri-axle buses up to 50mph. But in April, operator Stagecoach rolled out an automatic speed restriction system on 30 buses. It’s said to be the first such implementation of the technology in the UK.
There were three reasons for installing the system, according to engineering director Terry Absalom: general safety in the area where the vehicles are travelling, reducing speeds to improve safety and the comfort of the ride. “We are always looking to improve the safety and comfort of our passengers and drivers, particularly when the technology is already there.”
Because the area is boggy fenland, the busway supporting piles have a tendency to settle into the ground, creating uneven bits that create bumps. For this reason, Stagecoach imposes speed restrictions on sections of the busway. (Not that it has any concerns about the busway’s longevity, he points out. In fact, if a section sinks too much the council will close a section for a few days to insert shims to raise it up.)
Stagecoach had previously imposed a 30mph speed restriction over the entire southern section, and there are now some 20 speed restrictions of various levels on the northern section; some are where the busway crosses public roads (which are traffic signal-controlled, and automatically sensing an arriving bus and switching the lights in its favour). There are no speed restrictions on any part of the route off of the busway, except a 20mph limit at Cambridge North railway section where the northern busway section ends.
The system is based on Volvo Connect technology, the OEM’s condition monitoring system that records in real time vehicles’ state of health remotely, including operational parameters such as speed, throttle position, engine, gearbox, coolant and ambient temperatures. Buses are fitted with GPS trackers. On to them is uploaded a map of the route, including speed restrictions, which makes the route ‘geofenced.’ In other words, the vehicle interacts with the map automatically as it passes through it.
The Volvo Connect system tracks the location and speed of all of the buses in real time. Buses carry a map of geofenced speed-reduced areas. If a bus were to enter a geofenced area above the speed limit, the engine ECU works with the gearbox ECU and chassis I/O unit to initiate engine braking (and not the service brakes; see also pp28-30) to smoothly decelerate the bus. In speed-restricted zones, drivers are not able to raise the speed over the limit; during that time, the throttle goes dead. But of course they can still brake as usual.
Delayed by COVID, the system has been five years in the making. Initial talks began when Stagecoach was ordering a new consignment of buses from Volvo (only it and Scania are able to fit the guideway wheels, apparently). In the event, the operator ordered 12 tri-axle double-deckers and six single-deckers, augmenting its existing fleet of more than 30. Around that time, Volvo launched its Volvo Connect geofencing feature, and Volvo was confident it could support the software.
DELAYED BY COVID
The project start date had been set for March 2020, until the buses, and the project, were shelved because of COVID. When Absalom joined Stagecoach East a year later, MD Darren Roe tasked him with restarting the project. That responsibility fell primarily to Danny Smith, operations manager of the Fenstanton (Huntingdon) depot – and IT colleague Alex Vose, who worked with Volvo’s Phil Fletcher to set up the geofencing map, and in so doing teach themselves how the innovative system works.
Smith explains that they started with a digital overhead map of the route, upon which they drew boxes to designate speed-restricted areas. Once on the map, they can be resized by manually adjusting the area of the box by dragging at the corners. The process, it transpired, involved lots of trial and error, and ended up taking six months longer than intended. Absalom says: “It took hours and hours with laptops going up and down the busway, trying to understand why it wasn’t picking up the zones in some areas but it was in others.”
Hard-won lessons included the fact that the system needed to have a speed restriction in each direction. Also, they found that restriction boxes, even butted up next to each other, were clunky in operation; there was a noticeable jerk in bus motion as the bus’s engine brake kicked in to slow the vehicle. Fortunately, the team discovered that speed restriction boxes could be laid on top of each other, and the overlaps create a more gradual phasing of speed restrictions.
Along the route, signage reminds drivers of restriction zones coming up, not that bus drivers need them, given their extensive experience of the route, as well as the training that they received. Smith adds: “The system is in as a backup, so drivers are generally off of the throttle, slowing down, before they enter a zone.” The depot team has also designed detailed back-up routes in case a section of busway is shut. This ensures that even a diversion won’t stop the buses from being picked up by the system, which requires each bus to travel through a fixed activation zone (designated on the map by a circle).
In April, these extensive preparations were put to the test. Smith recalls: “Although this has been such a massive thing to implement, we had an uneventful launch. We were dreading the first day it was switched on. We got through the day with no phone calls. We asked ourselves, ‘Is it working?’ Nobody was complaining because everybody was trained, knew what they needed to do, and they knew we weren’t asking for them to do anything different.”
Now that the system is fully operational, Absalom is keen to point out its potential elsewhere, such as in city centres, near busy schools or road hazards, or points of dense traffic.
He concludes: “I am sure that we are looking at how to implement it elsewhere in the company. This has opened up a massive opportunity not just for us but for other operating companies that have these technologies and this capability. We’re just pleased to have done it first on a busway in the UK.”
BOX: SERVICING GUIDE WHEELS
Every service, engineers check that guide wheels aren’t touching the sides of the busway or out of line. To this end, Stagecoach installs a spring-loaded gauge on each wheel; they have only a 2mm operating tolerance around the ideal distance of 2,605mm. Any more than 2,607mm is too wide, and risks damaging the tyres. Less than 2,603mm is too narrow, and risks bouncing.