Background
Polmont is a town of 5040 people (as of 2020) in central Scotland, located in the Falkirk-area 35km/22mi west of Edinburgh and 35km/22mi east-northeast of Glasgow (both measurements in linear distance).
The town has a station on the Glasgow-Falkirk-Edinburgh line, a double-tracked at the time unelectrified main line connecting the country’s biggest cities. Opening in 1842 the line is one of five rail-connections between Edinburgh and Glasgow and is usually considered the main corridor between the cities. At the time the line was used by both regional passenger services and high speed Intercity Services connecting Glasgow to London (England).
The train involved
The 5:30pm connection from Edinburgh Waverley Station to Glasgow Queen Street Station was an express passenger service provided by ScR (British Rail Scottish Region) consisting of a locomotive, four Mark 3 passenger cars and a Mark 2 cab-car (called DBSO) from where the driver controlled the locomotive at the back of the train. Push-Pull trains are nothing new, having been around since at least 1906. They consist of a dedicated cab-car placed at the far end of the train, that being a passenger or freight car which features a more or less complete driver’s cab to control the locomotive when pushing the train. The main purpose is the ability of simply having the driver run down the length of the train at the terminus, board the cab-car and drive the train the return trip, instead of having to uncouple the locomotive and move it to the other end of the train, which requires time, resources and infrastructure (a push-pull train can reverse direction at any point, no siding or shunting is required).
The DBSO-series of cab-cars was introduced in 1979, with 13 units being created by modifying retired Mark 2 passenger cars. During the modifications the cab-end was fitted with driving controls, the passageway was removed and lights along with a horn were added to the front of the cab car. Each DBSO measures 20.12m/66ft in length at a weight of 33.5 metric tons and can reach 160kph/100mph. They still seat passengers in about half the interior, with the other half being dedicated to the driver’s cab. The unit involved in the accident was number 9706, the sixth one made, created in 1979.
Pushing the train from the back at the time of the accident was a British Rail (BR) Class 47 locomotive. Introduced in 1962 the Class 47 is a six-axle multipurpose diesel locomotive developed for both passenger and freight services. Each Class 47 measures 19.38m/63.7ft in length at a weight of 127 metric tons. The locomotives are powered by 2050kW/2750hp twin-bank 12-cylinder diesel engine and could reach up to 153kph/95mph. The Class 47 involved in the accident was number 47707, one of seventeen specially modified for the Glasgow to Edinburgh services. The locomotives, designated 47/7, were fitted with larger fuel tanks and the needed equipment to be remotely operated from a cab-car. They were also supposedly able to reach 160kph/100mph. Their introduction in 1980 simplified operation of the Glasgow to Edinburgh service, which had previously operated by sandwiching a row of train cars between two Class 27 locomotives.
The accident
On the 30th of July 1984 Mister Tennant is driving the express service from Edinburgh to Glasgow near the town of Palmont. So far the trip has been uneventful for him and his approximately 150 passengers, one of countless evening shuttle services between Scotland's largest cities. At 5:52pm the train is passing through Polmont at approximately 144kph/90mph. Leaving Polmont behind the train navigates a left turn, which is when Mister Tennant spots an obstacle just a short distance ahead. A cow, later determined to be a Ayrshire weighing around 400Kg/880lbs, is standing on the tracks.
Mister Tennant immediately triggers an emergency stop, but it’s too late to avoid the collision. The brakes on the DBSO apply right away, but due to the remote-control system the locomotive keeps pushing from behind, giving the passengers a jolt, before its brakes apply as well. Despite Mister Tennant’s best efforts his train hits the cow at 5:55pm, travelling at 137kph/85mph on impact. The cow dies in the collision, but a piece of the body (later declared to likely be a leg bone) gets jammed beneath the train in such an unlucky way that it lifts the forward left wheel out of the tracks. The DBSO leaves the tracks to the left as the rear end rotates 180° around the front, running up a slight embankment and falling over as it separates from the train, losing its bogies in the process. The following car’s front end digs into the soft ground with such force that it cartwheels end over end, coming to a rest upright and on the oncoming track with severe damage. The remainder of the train derails as well but remains right side up with varying degrees of damage. Mister Tennant survives the collision with severe injuries, being one of 61 injured survivors (17 of which being severely injured), but 13 people die as they are ejected from the train or suffer violent impacts with the inside of the train cars.
Aftermath
Responders from the nearby town of Polmont reached the site within a few minutes, using a gap cut into the wall running along the tracks by the cartwheeling second car to access the wreckage. Most fatal and severe injuries had occured in the second car, despite most of its body remaining intact, with the leading DBSO faring second-worst as it suffered a significant amount of deformation from running into the embankment and falling over, along with being rear-ended by car 2 before it broke free. Most victims were found outside the train, having been ejected from shattered windows or through the passageways as the train cars disconnected. This revelation led to calls for seatbelts to be introduced aboard trains, something shot down by the official investigation as essentially unenforceable, not to mention impractical.
Investigators found that the cow had most likely entered the rail line through a collapsed piece of the rockwall running along the tracks a short distance away from the site of the collision. The report notes how gaps in the fences and walls along Scottish rail lines keep being reported, often being linked to vandalism rather than wear. There had been seven incidents in the area over the past five years where cattle had wandered into the path of trains and gotten struck, but so far the only fatality had always been the cow. According to the engineer in charge of maintaining the fences and walls in the area, which belonged to the district rather than the rail company, the vandalism could be difficult to keep up with. Any spotted damage would be reported by the railway staff to the council who would organize temporary repairs until fences and walls could be properly reconstructed. However, at times damage would appear faster than it could be fixed. Despite this recurring problem there was no doubt in the section’s approval for 161kph/100mph speeds as, technically, the line was safe and fences were up to the requirements for those speeds.
The report has no choice but to conclude that, in essence, a chain of “bad luck incidents” caused the accident, and that no-one is really to blame. A cow wandered through a random gap in the fencing, which keep appearing despite the best efforts of the railway company and local district, and just happened to end up not on another meadow but in the path of a speeding train. The report calculates that Mister Tennant spotted the cow at a distance of under 500m/1640ft, giving him about 12 seconds to react. In that time he had a choice of retreating to try minimizing his injury, or trying to slow the train at least a little bit.
A veterinary expert asked to weigh in on the investigation concluded that an impact at the calculated speed with that kind of a train would disintegrate the animal rather than running over it, pointing out that the most likely piece to cause the accident would be the hind leg which might be left more or less intact. He noted that there was next to nothing of the animal left on the remains of the forward car, suggesting that, had the train missed the suspected large bone, it might have proceeded through the collision without much incident, except for some impact damage to the front end.
As it happened the veterinary expert explained that certain bones of a cow like the one involved in the accident are tough enough to overcome the DBSO’s wheel load of 4.5 metric tons for long enough to lift the wheel past the 45mm-mark, which is sufficient to move the wheel out of the tracks. This finding once again called the safety of push-pull trains into question, which have the heavy locomotive at the back pushing a relatively light vehicle up front. The question had previously been raised after the investigation looked into the delayed braking, but the delay they calculated was so minor that it played no role in the accident. However, the report pointed out that the safety of pushed trains had been thoroughly investigated before their introduction, and that the locomotive pushing at the back could in no way “buckle” the train by pushing into a decelerated (crashed) cab car. The report did admit that a lightweight train car is obviously easier to force out of its track than a locomotive, which was a matter to be addressed, but the difference was deemed small enough to not render push-pull services unsafe.
As such the report closed with two recommendations:
- Fencing along livestock-pastures adjacent to rail lines was to be improved to make them harder to collapse on purpose or by accident
- Object deflectors capable of pushing smaller obstacles out of the way were to be fitted to any leading rail vehicle with an axle load below 16 metric tons. Had the train involved in the accident been fitted with those it may have been able to shove the cow’s remains aside.
The recommendations were adopted and nowadays having some sort of object deflector is a standard requirements for cab cars and locomotives across Europe. In countries that see snowy winters they are often designed to serve double-duty as deflectors but also to clear excess snow off the tracks ahead of the train. They do have to keep a slight distance from the tracks so they don’t get stuck on infrastructure or in poor trackage.
After the accident the leading two cars remains were cut up on site before being hauled off for scrap, the rest of the train was placed back on the rails and towed away. With unit 9706 being gone another DBSO was constructed and introduced into service in 1986 as unit 9714. As of 2022 the type is still in limited service, while 2 units have been preserved and another 4 are in service as cab-cars for maintenance and testing-trains. While most services on the Glasgow-Edinburgh-line were taken over by Class 385 multiple units after the line’s electrification in 2017 push-pull trains with traditional locomotives are common all over the world and won’t go anywhere for the foreseeable future, which leads to their safety regularly being called into question after a pushed train’s cab car derails.
In 2009, on the accident’s 25th anniversary, a memorial plaque was unveiled at nearby Polmont station, reminding the public of the victims and survivors of the accident as well as thanking the responders and railway workers involved in the rescue, recovery and repair operation.
The site of the accident has changed quite a bit since the accident, with a whole new district of residential housing being built where the cattle-pastures used to be. Accidents between livestock and trains still occur every now and then, but with few, tragic exceptions they usually cause little more than material damage and delays.
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