We’re asking passengers for feedback on major proposals to unblock a railway bottleneck at Croydon until September so we can provide more reliable, more frequent and faster train services.
The Croydon area on the Brighton Main Line is very busy. Here, lines from the south coast, Sussex and Surrey meet those from London Victoria and London Bridge.
To help the traffic flow, we’re hoping to build extra tracks; provide more platforms and modernise East Croydon station, and build a series of railway flyovers and dive-unders to replace the current congested junctions.
What exactly is a bottleneck on the railway and how do we get rid of one?
It’s a constraint in the infrastructure that limits the number of trains able to pass through an area. For example, the number of tracks or the capacity of the signalling or power supply systems, which limit the number of trains the area can accommodate.
We identify a bottleneck as a section of railway where it would be possible to run more services if we resolved the problem.
In normal times, the railway is very busy across Britain. Does that mean there are bottlenecks everywhere?
It’s all about supply and demand. We only identify a bottleneck where there is a desire to run more trains than currently possible. That means there are no bottlenecks on quieter routes where there is less demand for passenger and freight services.
In the case of the Brighton Main Line, more than 1,700 trains and 300,000 passengers a day travel through the Croydon area in normal times.
A significant number of services, particularly during peak times, are usually overcrowded. This is because we can’t fit any more trains on the normal timetable because the current track layout, signalling system and station platforms are already at capacity.
The track layout in the Croydon area is also composed of multiple flat junctions, where trains are held at red signals while others cross in front. This significantly impacts train performance as well as capacity – knock-on delays are often caused by trains arriving late into the area.
Trains must also split and join at stations to the south to reach their destinations because the number of train paths through Croydon into London is limited. This often delays journeys.
Why do we have bottlenecks in the first place?
Britain’s railway was mostly built during Victorian times. The existing infrastructure was simply not designed for the number of trains and people who typically use it today.
How do we determine which bottlenecks to remove?
We remove a bottleneck when we have exhausted all other options to improve services.
The rail industry is always looking at the long-term needs of the railway. This planning involves detailed analysis that forecasts future passenger and freight usage by region. It’s based on factors such as population and economic growth, employment, and government environmental and transport policy.
We develop options to provide more capacity when forecasts show we need to. Where possible, we propose longer trains and timetable changes because they’re often quicker and more cost-effective than construction. When this isn’t possible, we propose bigger infrastructure-based solutions to unblock a bottleneck.
In the case of the Brighton Main Line upgrade, trains have already been lengthened to the maximum 12 carriages on most peak time services and the normal timetable provides the most trains possible through the Croydon area.
This means we wouldn’t be able to avoid delays and overcrowding in the future without making big changes to the infrastructure.
What are the main things we take into account when redesigning a section of railway like this?
The aim is two-fold – we must come up with a design that enables more trains while also reducing delays to passengers.
In the case of the Brighton Main Line upgrade, the solution we’ve identified includes more platforms at East Croydon station, new tracks and flyovers and dive-unders to separate the tracks through the area.
The design must also be safe and high-quality and minimise disruption during construction. We need to have decided how to reduce the impact on passengers, communities and the environment before we can start work.
In the Croydon area, it’s vital we can ensure as full a train service as possible during the project – this has driven the proposed design and construction methodology.
Infrastructure solutions also need to offer value for money to the funder. We produce a business case that includes anticipated value for money, which we calculate by comparing the total cost with the benefits.
You can view our proposals for unblocking the Croydon bottleneck and provide feedback via our survey here.