Could a Croydon Tram Accident Happen?

In the aftermath of the Croydon Tram incident, many questions emerged. The Rail Accident Investigation Branch (RAIB) report states: “The RAIB’s investigation concluded that it is probable that the driver temporarily lost awareness on a section of route on which his workload was low. The investigation has found that a possible explanation for this loss of awareness was that the driver had a microsleep, and that this was linked to fatigue.” To explore whether a similar event could happen on our network, see Could a Croydon Tram-style accident occur on Metrolink?

Union Agreement Changes and Impact on Driver Fatigue

Previously, Metrolink operated under strict parameters governing duty lengths and rest periods, offering better protection than legal minima. However, Unite signed away these safeguards, allowing the operator to:

• Extend average duty lengths from 7.5 to 9.5 hours.
• Permit drivers to work up to 5.5 hours without a break, instead of between the 3rd and 5th hour.
• Ignore up to two hours of daily commuting when planning shifts.

These changes increase fatigue, elevate the risk of microsleep, and raise the likelihood of incidents involving tired tram drivers.

Why Was Safety Compromised?

Why did Unite agree to a deal that increases working hours and delays breaks, when other unions are striving to reduce fatigue and enhance public transport safety? The answer remains unclear, but the consequences for driver well-being and passenger safety are evident.

RAIB Investigation Details

Accident Summary

On 9 November 2016, tram 2551 entered a sequence of tunnels at 80 km/h. Exiting the third tunnel, it failed to decelerate for a 20 km/h curve at Sandilands junction and was travelling at 73 km/h when it reached the speed-limit sign. The tram overturned, killing seven passengers and injuring 61 (19 seriously).

Investigation Methods

• Data extraction from the tram’s on-board recorder and signalling system
• Tests on safety systems
• Computer modelling of overturn speeds
• Infrastructure design review
• Safety and risk management audit
• Interviews with personnel and organisations
• Driver surveys on route operations

Key Findings

• No means to monitor driver alertness or automatically apply brakes when overspeeding
• Inadequate signage for braking zones and curve warnings
• Window failures allowed passengers to be ejected, causing fatal or serious injuries
• Poorly distinctive tunnel features led to driver confusion regarding location and direction

Recommendations

The RAIB issued 15 recommendations to improve tram safety, including:

• Implementing automatic braking and alertness monitoring systems
• Developing guidance on non-road tramway risks
• Enhancing door and window strength
• Strengthening safety management culture to encourage reporting of errors
• Reviewing tramway regulation and considering a dedicated UK tram safety body

Video Summary and Animation

Overturning of a tram at Sandilands junction, Croydon
Watch animation and timeline

Animated recreation of Sandilands derailment
Play animation with WAI-ARIA timeline

Definition: Microsleep

Microsleep – Unintentional periods of sleep lasting a fraction of a second up to a few minutes, often marked by eyelid closure or head nodding. These episodes can severely impair a driver’s responsiveness and awareness.