TSB Recommendation R22-02

The issue of uncontrolled movements of railway equipment is not a new one. The TSB has pointed out the need for robust defences to prevent uncontrolled movements since 1996. On 12 August of that year, all 3 occupants in the operating cab of a locomotive were fatally injured when their train collided head-on with a cut of 20 runaway cars near Edson, Alberta.^{Footnote 1} In its investigation report, the TSB indicated that the facts surrounding this occurrence raised some concerns, notably with respect to the secondary defences against runaways.

The issue came to the forefront again in 2013 when, on 06 July, a runaway train derailed in the centre of the town of Lac-Mégantic, Quebec, destroying the town’s core and main business area, and causing the death of 47 people.^{Footnote 2} In its investigation report, the TSB indicated that equipment runaways are low-probability events that can have extreme consequences, and the cost to human life and our communities can be incalculable. For this reason, the Board recommended that

Since then, the trend in the number of uncontrolled movements has been on an upward trajectory. In 2014, the year after the Lac-Mégantic accident, there were 59 occurrences; in 2019, there were 78, including this one. Unplanned/uncontrolled movements of railway equipment remains a current issue and is included in the TSB’s Watchlist 2020, a list of issues that need to be addressed to make Canada’s transportation system even safer.

In the years since Recommendation R14-04 was issued, in an effort to address these concerns, Transport Canada (TC) has implemented several initiatives aimed at reinforcing and clarifying requirements in the Canadian Rail Operating Rules (CROR) governing the application of hand brakes. These initiatives included a revision to Rule 112 in 2015, which provided the industry with a comprehensive hand brake application chart to respond to various operating situations when securing unattended equipment.

Following the occurrence at Field, TC again modified the CROR with new requirements for the use of hand brakes. It introduced Rule 66 (Securing Equipment after an Emergency Brake Application on Grade) for the securement of trains stopped in emergency on heavy grades and mountain grades.^{Footnote 3} The new rule also includes a comprehensive hand brake application chart. It came into effect on 24 June 2020.

A hand brake is a mechanical device used to secure railway equipment and prevent uncontrolled movements. Hand brakes are installed on all railway rolling stock. They are manually applied and tightened by turning the hand brake wheel. This causes the brake shoes to be pressed against the wheel tread surface to prevent the wheels from moving or to retard their motion.

For hand brakes to securely hold a train, the right number of them must be applied to generate the needed brake force.

The hand brake application chart in Rule 66 indicates the number of hand brakes that must be applied on a train based on train tonnage and descending grade. For instance, given the occurrence train’s weight of approximately 15 000 tons and the average 2.2% grade on Field Hill, to meet the requirements of Rule 66, it would have been necessary to apply 75 hand brakes on the train after it had stopped in emergency.

There are several factors, however, that can reduce the effectiveness of hand brakes, most notably low input torque (the amount of force applied by the operator at the hand brake wheel), service wear, and reduced coefficient of friction (COF) of the brake shoes from rail conditions such as the presence of ice or snow. When some of the hand brakes on a train are not fully effective, more hand brakes are needed to achieve the brake force necessary to hold it stationary.

In practice, operators do not know how much force they are applying at the hand brake wheel, as hand brakes do not provide this type of feedback. Nor do they know the coefficient of friction of the brake shoes, or whether a hand brake’s effectiveness is reduced due to service wear. The only available means to determine whether a sufficient number of hand brakes has been applied, therefore, is to perform a hand brake effectiveness test. This test involves releasing the air brakes to confirm that the train does not begin to roll. If the train does roll, more hand brakes must be applied, and the test performed again. In the operating scenarios covered by Rule 66, however, this test is not feasible for a train stopped on a heavy or mountain grade. In such circumstances it would be highly risky to release the air brakes, as the train could begin to roll quite quickly and it may not be possible to stop it again. Therefore, operators must rely on the pre-determined number of hand brakes mandated by the rule. If some hand brakes on the train are not fully effective, this number may not be enough, and there is a risk of uncontrolled movement.

Applying hand brakes is physically demanding and time consuming. Operators must board the car by climbing the side ladder, position themselves safely at the hand brake wheel, and crank the wheel clockwise to take up chain slack before applying maximum force on the crank. They must then dismount, walk to the next car, and repeat the manoeuvre. Applying a large number of hand brakes requires a sustained effort over several hours. As fatigue sets in, the force that operators are able to exert at each hand brake wheel may diminish over time; with lower input torque, the effectiveness of the hand brakes is reduced, requiring more hand brakes to be applied.

Table 28 shows how many hand brakes would be needed to hold a 15 000-ton train on a 2.2% descending grade, assuming 55 foot-pounds input torque (the force achieved by the participants in the human performance assessment),^{Footnote 4} and a coefficient of friction in the range of 0.3 to 0.4. In the presence of brake cylinder leakage, an increasingly higher number of hand brakes would be needed as the pressure drops. According to this table, the 75 hand brakes mandated by Rule 66 would be sufficient, based on a COF of 0.39, and a BCP of 10 psi.

As the table shows, the number of hand brakes needed to hold a train varies greatly based on several variables, over which train crews have no control.

Table 28. Number of hand brakes required at an input torque of 55 foot-pounds to hold a 15 000-ton train on a 2.2% descending grade, based on the coefficient of friction of the brake shoes and the average brake cylinder pressure*

Coefficient of friction	Number of hand brakes required based on average brake cylinder pressure
	77 psi**	65 psi	50 psi	35 psi	25 psi	10 psi	0 psi
0.30	42	40	46	55	67	102	162
0.31	40	39	44	53	64	98	156
0.32	39	37	43	51	62	95	151
0.33	37	36	41	50	60	92	146
0.34	36	35	40	48	58	88	141
0.35	35	34	38	46	56	86	136
0.36	34	33	37	45	54	83	132
0.37	33	32	36	44	52	80	128
0.38	32	31	35	42	51	78	124
0.39	31	30	34	41	49	75	120
0.40	30	29	33	40	48	73	116

* The numbers in this table assume a net hand brake ratio of 6.5%.
** A brake cylinder pressure of 77 psi corresponds to the pressure after an emergency brake application, when there is no brake cylinder leakage.

There is AAR-approved technology available for securing trains, which takes most of these variables out of the equation: automatic parking brakes for rail vehicles (APBs), such as Wabtec’s Automatic Park Brake and New York Air Brake’s ParkLoc. APB technology has been tested and approved for use on North American railways, but it has not been widely adopted.

APBs are brake cylinders equipped with an automatic, mechanically operated latch that locks the brake cylinder piston as needed depending on the pressure in the brake pipe. When the brake pipe pressure is depleted (e.g., after a penalty or an emergency brake application), the system automatically locks the brake cylinder piston in the extended position, thereby retaining the brake force. This occurs without any specific intervention or action by the train crew. Once the brake pipe pressure increases again, the system automatically releases the lock and retracts the brake cylinder piston, which releases the brake force. APBs can be configured for use on both truck-mounted and body-mounted brake systems, and they can be retrofitted on existing freight cars with no need to make modifications to the air brake system.

Because APBs lock the brake cylinder piston into position on the cars, their effectiveness is independent of input torque, and it is not affected by brake cylinder leakage. APBs, therefore, can hold a train on a steep grade indefinitely.

Uncontrolled movements of railway equipment, while low frequency events, can create high-risk situations that may have catastrophic consequences. TSB investigations into uncontrolled movements have revealed that the sequence of events almost always included inadequate train securement. TC has made several improvements to the rules governing the application of hand brakes. However, even with a comprehensive set of rules, it has been demonstrated over the years that depending solely on the correct application of rules is not sufficient to maintain safety in a complex transportation system. The concept of “defence in depth” has shaped the thinking in the safety world for many years. Layers of defences, or safety redundancy, have proven to be a successful approach in many industries, to ensuring that a single-point failure does not lead to catastrophic consequences.

Better and more numerous administrative defences have not been successful in establishing safety redundancy against uncontrolled movements. To date, the Canadian railway industry and the regulator have yet to look beyond strengthening an administrative defense such as the use of hand brakes.

Until physical defences such as automatic parking brakes are implemented across the Canadian railway network, the risk of uncontrolled movements due to inadequate train securement will persist, especially on steep grades where the effectiveness of hand brakes cannot be tested.

Therefore, the Board recommended that the Department of Transport require Canadian freight railways to develop and implement a schedule for the installation of automatic parking brakes on freight cars, prioritizing the retrofit of cars used in bulk commodity unit trains in mountain grade territory (TSB Recommendation R22-02).