Buses versus Trams – why Automatic Vehicle Location Control systems need to know the difference

Published December 15, 2020 in Blog

In a comprehensive transport network, a combination of trams, trains, ferries, and buses are commonly used to deliver quality passenger journeys. It is pretty obvious that rail and road are different forms of transport, but light rail and trams are not buses.

So, when looking at procuring an Automatic Vehicle Location and Control (AVLC) system it is important to understand:

    • What these differences are
    • How they impact on your ability to monitor and control your fleet in real-time, and
    • The importance of working with a partner who has extensive experience in delivering AVLC systems in both the bus and tram domains.

Go anywhere!

Clearly, having a steel track built into the road is a major differentiator between buses and trams. Trams are constrained to run on their tracks only, whilst buses have the freedom to reach into the suburbs, vary the route on the fly, and travel over any road. Well, almost any road – buses designed for rapid transit (Bus Rapid Transit, or BRT) often load at a central stop (with the doors on the other side of the vehicle to normal route buses) and are thus restricted to these corridors.

Articulated buses cannot go into some streets due to their larger turning circles (although some do try), and double-decker buses cannot pass under all bridges.

Planning systems should be able to avoid some of these mistakes, and a dynamic vehicle tracking system can also alert drivers when they are off track or in a forbidden zone for that vehicle type. But it can still happen if the right systems and controls are not in place!

Running methods

Limited by tracks, trams are far more susceptible to disruptions than buses, as a car that is even partially overhanging the track in an accident can stop all the trams that use that track – whilst a bus will just drive around the accident. To deal with this, trams have developed different modes of operation that are not needed for buses – for instance, single track running, short working, or curtailment. AVLC systems used for trams need to be able to cope with these additional running methods and need to show track junctions, so operators can see where to run their vehicles.

Tracks also bring with them the need to select point positions to navigate the path. Interfacing to the point control hardware and having the necessary route information to decide which way to switch the points is critical to this operation – and requires the right AVLC hardware and software.


Trams have a larger capacity than buses. This means your AVLC system must be able to cope with more than just additional CCTV cameras and passenger information displays. It means it must be able to cope with multi-door boarding, as well as knowing which side of the vehicle the doors are going to open. The AVLC also needs to inform passengers of this information in advance through automatic passenger announcements.

For trams, passenger counting systems need to be able to cope with multiple entries and exits. Announcements may contain stop level information critical to some passengers – such as the absence of a platform at the next stop, which means a lack of accessibility for wheelchair users.


In Australia, most, if not all trams are bi-directional – so we need to know about track switches to safely change direction. In Europe, trams can also be unidirectional, so the AVLC needs to know of the presence of track loops to support a return journey.

Bi-directional trams are more complex, as the AVLC system not only has to support two driver control heads, but also have the smarts to allow the driver to simply change cabs at the end of each trip. With the change completed, all control will vest with the driver, and headboards will show information for the new direction.

Trams can also be joined in a consist to effectively carry more passengers. When this happens, the AVLC system on each tram needs to be connected, so that passengers in any car in the consist receive the same information and messages. The Trapeze Wire Train Bus is an IEC 61375 compliant hardware set, proven to meet the needs of this connection in a tram environment.

With the tram sets connected, it is important to show back office dispatchers which tram is the lead tram, and which are the following trams. Another factor to consider when combining trams – it is important to attribute all the collected data and statistics to the correct trips, routes, or vehicles, for example, the passenger counters located throughout the tram. In the second set of carriages, the count information is collected and needs to be passed to the master, so it can be recorded against the actual trip being operated.


Physically, equipment that operates in a tram needs to be rated for the shock and vibration levels experienced on a rail-based system – therefore, certification to EN50155 is essential. In a similar vein, the tram equipment must be protected against electromagnetic interference from the power systems, and electromagnetic compatibility with other devices is just as important. Equipment that meets the tram environment requirements will work in a bus, but since bus equipment is typically made at a lower price, this is not always true the other way around.

Tram wheels also have special needs. In an icy environment, it is common to lay sand on the track for traction. The wheel flanges also need regular lubrication, and the AVLC system can be used to drive this lubrication based on tram location, and distance run.

Traffic signal priority

Both buses and trams can benefit from timely and effective traffic signal priority. However, with their larger passenger capacity and inability to navigate past traffic, trams are particularly vulnerable to even small traffic disruptions. So, giving trams an early start via a dedicated tram movement, can get them ahead of the traffic flow and make a big difference to their on-time running – and should be part of any AVLC system.


Generally, GPS can be used for determining tram location. However, this is not sufficient for resolving which track the tram is on, when the two tracks are only a couple of metres apart. AVLC should not be considered a safety system. However, it can use information from a train control system to locate the vehicles on their exact track sections, and then use this for passenger information, as well as detecting if the vehicle is driving on the opposite track. This information can also be used to determine the exact vehicle sequence when a vehicle approaches a tram stop, as well as updating passenger information at the stop.


When there is an accident that blocks part of the road, a path diversion for a bus is fairly straight forward with alternate routes aplenty. For a tram, this is not so straight forward. There is often a need to assist dispatchers by specifically representing the tram networks in the control room interface, showing critical paths and connections.

Trapeze is working with our tram customers on ways to show this, such as this dead running graph that includes a driver cab change.

Trapeze is also working on illustrating junctions along the routes, and vehicles on the junctions. This is a functional extension of the standard route diagram, that provides critical information to tram operators and looks similar to this:

We are also able to show detours with track changes (shown in red). This gives dispatchers a clear picture of what is happening on the street.

Recent work at Trapeze is exploring a schematic network diagram that shows routes/stops etc. in a pseudo geographical way. This makes it easier to conceptualise the operations across the city as it shows the relationships between the lines.

Many systems use both bus and tram modes, but there are cities with tram only systems, such as Hong Kong and Lisbon.


The right AVLC system can help you deliver real-time information and control to your transport fleet. This can significantly improve the service you offer your passengers and deliver efficiencies and cost savings directly to your operation.

AVLC systems benefit tram operators because:

    • A solution that has evolved with decades supporting tram operations
    • The solutions continue to grow based on feedback from tram operators on the unique needs of tram operations, and
    • The system supports tram specific features that are proven in tram operations.

We have discussed some of the tram features you should look for when selecting your AVLC system in this article – so that you can successfully operate a fleet of trams or a mixed, multimodal fleet of buses and trams.

Mode of Transport

Bus, Trams/Light Rail, Ferry


Intelligent Transport Systems

Meet the author

David Panter

Industry Solutions Manager, ITS

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