The curious case of the Class 805 improvement notice

The Health and Safety at Work Act gives inspectors powers to issue prohibition and improvement notices. Prohibition notices are issued when it is considered necessary to stop an activity that involves risk of serious personal injury. Such notices must state the cause of this risk and the legislation that has been breached. When an improvement notice is issued, the inspector must specify which legislation has been breached and specify a time for compliance. Improvement notices are not required to state the risk associated with the legislative non-compliance.

In August 2024, the Office of Road and Rail (ORR) had issued Avanti West Coast (AWC) with an improvement notice in respect of the operation of its new Class 805 which had received authorisation to operate from the ORR in December 2023. AWC has appealed against the issue of this notice which as a result has been suspended during the appeal period.

Authorisation to operate

The documentation submitted to the ORR to receive authorisation to operate the Class 805 includes a safety assessment report. This contained a risk assessment undertaken in accordance with the common safety method (CSM). This is a rigorous hazard identification and risk assessment process as specified in the relevant legislation. For each identified hazard, an assessment is required of whether it is broadly acceptable and, if so, a justification for this decision. If not, the risk from the hazard needs to be estimated and evaluated to specify the required safety controls. The ORR authorises a new train to operate after it has reviewed the required documentation and found it to be satisfactory.

So why, eight months after it accepted the Class 805’s safety assessment report, does the ORR now consider that the operation of these units breaches legislation? Although the improvement notice specifies which legislation has been breached, this is not currently in the public domain as AWC has appealed against the notice. When asked to comment, the ORR provided the following statement:
“ORR has issued an improvement notice to Avanti West Coast (AWC) because, unlike existing trains they are replacing, the new Class 805 trains are not fitted with an automatic speed supervision system.”

TASS

The Class 805 units are replacing Class 221 diesel units. Like the Class 390 ‘Pendolino’ trains, the Class 221 units are tilting trains that operate on the West Coast Main Line (WCML) and are fitted with a Tilt Authorisation and Speed Supervision (TASS) system. This has balises on the track that send signals to the Class 221 and 390 units to manage their speed and tilting. Due to their ability to tilt, the units can run around curves at up to 125mph. The Class 805 units normally operate on the south end of the WCML where non-tilting trains are limited to a maximum of 110mph.

Although TASS was installed to enable operation of the tilt mechanism, it also provides an automatic speed supervision system, a form of continuous speed supervision unlike the intermitted approach of the Train Protection Warning System. Hence it could be considered that TASS provides a greater level of safety. Readers can judge for themselves the extent to which TASS reduces risk reduction from the information below.

The new Class 397 units operated by TransPennine Express (TPE) on the WCML are not fitted with TASS and are not the subject of an improvement notice. This shows that the ORR’s concerns about fitting TASS to new trains solely relate to AWC operations as TPE drivers do not drive at the higher curving speeds of tilting trains. Furthermore, as AWC drivers will now alternate between TASS-fitted and non-TASS-fitted trains there is a possibility of an overspeed if, when driving a Class 805, drivers forget that it is not TASS fitted.

Level of risk

The reason that tilting trains can operate around curves at such higher speeds is that, for the comfort and safety of those inside the train, tilt reduces the centripetal forces on them as the train goes around a curve. If a non-tilting train goes around a curve at 125mph instead of 110mph, people and objects inside the train will experience a 29% increase in centripetal force as this is proportional to speed squared.

However, there is no risk of the train coming off the track as a result of such overspeeding as tilt does not affect lateral track forces. Hence, the curving forces on the track for a Class 805 at 125mph would be very similar to those from a tilting Class 221 at 125mph. If there was any risk of such an overspeed resulting in a derailment, the ORR would have issued a prohibition notice rather than an improvement notice.

Thus, the risk of a Class 805 overspeeding because it is not fitted with TASS is to those inside the train. This hazard should have been identified with the level of risk and required safety control shown in the CSM risk assessment. Although Rail Engineer asked the ORR and AWC whether this hazard had been identified, neither were prepared to comment on this issue.

A change of mind?

The issue of an improvement notice some months after authorising the Class 805s to enter service shows that the ORR has either:
Now identified that the overspeeding hazard was missing from the CSM risk assessment and is retrospectively rectifying this deficiency by the issue of an improvement notice.

Changed its mind and no longer considers that the overspeeding risk assessment shows that the specified controls manage this risk to a level that is as low as is reasonably practicable. Thus, it would seem that the ORR now considers AWC’s operation of Class 805 units now breaches the Health and Safety at Work Act.

As shown by its statement, the ORR’s particular concern is that a safety control (TASS) fitted to AWC’s existing fleet is not fitted to its Class 805 trains. Hence it would seem that compliance with the improvement notice, which is reported to have a two-year compliance period, requires the Class 805 to be retrospectively fitted with TASS or some other form of continuous speed supervision. As these units are ETCS ready, this may only require a software fix for the trains to receive TASS balise signals. If hardware modifications are required, the cost of compliance with the improvement notice could be significant.

As can be seen, the ORR’s issue of an improvement notice for the operation of a train that it has recently granted authority to operate raises various issues. It will be interesting to see how this curious case is resolved.

Image credit: Malcolm Dobell