Connection Protection: How AVLC systems get you home faster

Published September 07, 2020 in Blog

At first glance, connection protection may seem like a way to keep in touch with distant relatives, or possibly a dating app function to meet the love of your life, but it isn’t.

In the world of transport, it is a way to help ensure that passengers make their connecting services when interchanging on a public transport journey. (Connection protection is also known as transfer protection).

Imagine you are heading home, tired, weary. It is a cold and blustery evening and looking out of the tram you can see the rain running down the window.

Two more stops then a one-minute wait, and a ten-minute bus ride will end with a warm family dinner. But the traffic is heavy, and as you are still approaching the stop you can see your bus depart. Thirty minutes of standing in the rain and a cold dinner could have been avoided. If only the bus driver had known to wait!

ITS AVLC connection protection

The driver cannot make this call on their own. They need to focus on driving, and the complexities of the scheduling system mean it is not reasonable to expect drivers to know all the connecting services. Drivers normally cannot see the connecting services, so they need to be told how long to wait for the connection.

The control room operators may have full network visibility, but they are focused on network delivery and often have bigger issues than a single tram being delayed by five minutes.

What is needed is an automatic system that does not rely on human observation, that tells the drivers of those services, via a display on the dashboard, to wait for the inbound connection. Fortunately, these systems exist right now.

They are known as Automatic Vehicle Location and Control (AVLC) systems and are helping passengers reach their destinations efficiently and quickly in London, Singapore, Zurich and other leading world cities.

Then it predicts each vehicle’s arrival at every stop. Connecting services are examined and the drivers of these services are advised on a dashboard display when to depart the interchange. Departing services can be delayed to help commuters make their connections.

When setting up this connection protection there are some practical decisions that need to be made. First, we should ask ourselves, which services should wait for incoming passengers?

It seems obvious that a distributor bus service in the suburbs should wait for a full tram arriving from town in the evening. But what about inbound in the morning? Should the full tram heading to town wait for the bus if the bus is running late?

Trains only have a small scheduling window, and do not normally wait for late bus services. Deciding on which vehicle should wait is network and time of day dependent. Anticipated loads can also factor into deciding who should wait.

Once we know who is waiting for whom, how long should they wait? Every minute a departing service is delayed compromises the on-time running for passengers already onboard. Typically, operators are prepared to hold a bus for up to 2 minutes, but this will depend on the frequency of the service.

Less frequent services magnify the impact of missing the connection and a longer window may be allowed. Automatic thresholds can be supplemented with a manual override on selected routes – triggered only when the auto thresholds are breached.

Ideally, all transport modes are integrated and operate on the same system.

To work effectively, the system that is holding up the departing service needs to get real time information from the inbound service. The SIRI CP service is one way to do this. If they are on different tracking systems, then real time data must be shared in both directions.

What is also important for transport operators is to report on the missed connections. The connection protection can yield direct passenger benefits through time savings, but the reporting helps identify hot spots.

If certain services always just miss the connection, there might be a timetabling problem. Reporting allows planners to identify this situation and to make a small adjustment to one of the services so that in the future it is easier to make the connection.

Advanced AVLC systems inform passengers how their current and related services are running in real time, showing an updated connection status to passengers inside the vehicle.

This can be very valuable – we have even heard of passengers in Zurich looking at the display to work out if they can save a few minutes off their journey home by changing at an interchange to a different tram line.

They give operators the ability to dynamically control their fleet in real time and, with connection protection, they deliver a higher level of public transport service.

This modern transport technology is available now and ensures customers spend less time waiting for connections and more time on the things that are important to them. They can get home to a warm family dinner safely, conveniently and on-time because connection protection is working for them.

Mode of Transport

Bus, Trams/Light Rail, Ferry


Intelligent Transport Systems

Meet the author

David Panter

Industry Solutions Manager, ITS

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