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Dated driving policies found to increase operational risk
RSSB research requested by industry has revealed that current driving policies, especially those around braking, may have unintended consequences for whole-system risk.
Looking specifically at the delicate balance between the prevention of signals passed at danger (SPADs), train performance, and network capacity utilisation, RSSB investigated whether the established defensive driving instructions are still operationally suitable.
In particular, the project aimed to show how policy instruction changes could tell operators more about the likely impacts of different driving styles and shed some light on the importance of understanding—and operating in line with—system capabilities.
To learn more, the research team designed a number of microsimulations using RailSys—a widely used timetabling tool—to explore how different driving policy instructions affect performance and safety. Looking at Derby and a segment of the South Western Mainline between Woking and Wimbledon, the team found that:
‘Braking early and braking light’, one of the current driving policy instructions, caused lateness to rise by 10% compared with adopting a higher rate of braking.
This style of driving reduced the route capacity from 15 trains per hour to 13.
Because trains were taking longer to clear each signal section, this also led to 50% more instances of red aspect signals.
This style of braking, therefore, may increase the whole-system SPAD risk.
In the longer term, having access to this sort of predictive data could:
help operators better understand when and where significant delays are likely
determine how to manage the effects of those delays
provide more comprehensive information to the travelling public.
The reality is that some of the current driving policies, largely untouched since their introduction in the 1990s, can cause congestion on the network and possibly incur delay-related costs. This also means that current driving policy instructions may not be accounting for more sophisticated train braking systems, like sanders and wheel slide protection, or improved signalling system design that has emerged over the past 30 years.
Consequently, the capabilities of track and train infrastructure, the way timetables are designed, and how drivers are being told to drive their trains may not be optimal.
The findings of this research should support the creation and uptake of policies that are optimised to align with the system capabilities and available technologies. In an effort to improve the instructions available to their drivers, all GB passenger operators are already reviewing their respective policies.
To read the ‘Optimising driving policies’ (T1305) research in full, head to our Research Catalogue.
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