General

What is TubeNoise?

TubeNoise is an attempt to show the real-time position of tube trains on the Northern Line around Kennington.

I created TubeNoise after experiencing many years of problems with noise and vibration in my home caused by trains on the Northern Line. I realised that TfL's Trackernet Data Service could be used to show approximate train locations which would help diagnosing current and future problems with noise and vibration.

Why is it difficult to tube diagnose noise / vibration problems?

The TfL team need to identify which section of track is causing the problem.

In an area like Kennington this is particularly difficult due to the large number of tracks. The Charing Cross and City Branches of the Northern Line connect at Kenningon. There aren't double the number of trains going South to Morden - in fact most of the Charing Cross trains are turned around at Kennington and head back North on the Charing Cross branch. The trains are turned around on something called the 'Kennington Loop'.

In addition to the Kennington Loop, there is a siding which allows trains heading South to be turned around to head North on either the Charing Cross or City branches.

As a result there are a lot of tracks and connections around Kennington tube - making a quick diagnosis of the source of noise / vibration difficult for TfL / Tube Lines.

How accurate are the train positions?

There are two challenges in accurately positioning the trains on a map - determining the location of the tracks, and determining the position of the trains on the tracks at a particular moment in time.

TfL do not make publically available the locations in the ground of the actual train tracks so these need to be approximated from publically available sources. See the How It Works page for more information on how the track locations were estimated.

The Trackernet Data Service from TfL provides similar information to the display boards you see when taking a tube train. This is the estimated time in seconds before the train arrives in the station. This data is used to estimate how far along the tunnel the train is - and this is what you see displayed on the map. Often this estimate is wrong - a train stops in the tunnel or is held up at a station for longer than expected. In these cases the display will be wrong.

Overall, the train positions should be taken as an estimate.

Train Display

What do the red train segments represent?

Each red segment represents a carriage. On the Northern Line each train is made up of 6 carriages so you'll see 6 red segments. The segment length corresponds to the distance between the front and back wheels ('bogies') of each carriage. For the Northern line carriages this distance is 11 metres

The total length of a Northern Line train is 108 metres and the length represented by the 6 red segments is 101 metres - the distance from the first set of wheels on the first carriage to the last set of wheels on the last carriage.

Why do the train positions jump?

The train positions are updated every 30 seconds. At each update an estimate is made of where the train is now and where it is predicted to travel over the next few minutes. If the tube service experiences delays then the trains don't get as far as expected and the train position will jump back after the update. Sometimes the trains get further than expected and in this case the train position will jump forward.

The section of the tube network displayed includes the Kennington Loop. The length of time trains spend going around the loop varies widely which also results in the train positions jumping. Take a look at the How It Works page for more information on how the time on the Kennington Loop is estimated.

Train re-routing can also cause the trains to jump. Sometimes trains that usually go around the Kennington Loop and back to Waterloo carry on to Oval instead. Sometimes trains from Oval head to Waterloo as opposed to heading to Elephant & Castle.

If I click Pause, what does the number shown near each train represent?

This is the train's ID number - known as the LCID (Leading Car Identifier). This uniquely identifies each train on the line and is provided by the Trackernet Data Service.

Other

Do you have any plans to extend this service to other stations on the Northern Line or other tube lines?

Not at present.

June 2014