Railway Investigation Report
Safety Issues Investigation Report SII R05-01
Note that the data provided for some of these occurrences (that is, Class 4 occurrences) are based on a preliminary investigation only. Others (that is, Class 3 occurrences) were subjected to a full Board investigation. Therefore, the information available may not be consistent across all occurrences.
R03E0091 (12 October 2003), Derailment of 19 Cars on Canadian Pacific Railway (CPR) Train 269-11 at Mile 46.9 of the Aldersyde Subdivision
Eight of the cars contained anhydrous ammonia and seven contained fuel oil, but no product was released. The train was travelling at track speed, that is 45 mph. Weather was partly cloudy, windy with an ambient temperature of 15ºC. The primary cause was sections of broken out rail that created a 38-foot gap in the high rail of a four-degree left-hand curve. Rail was 1974 Algoma 115-pound continuous welded rail (CWR). High wheel impacts produced by the 15th car behind the locomotives were a significant contributing factor to the rail failure. The last rail flaw detection test before the derailment was done 30 July 2003. No internal defects were recorded within 10 miles of the point of derailment (POD). The next test was scheduled for the week of October 13.
On the Aldersyde Subdivision, 47 per cent of the rail was 1974 115-pound CWR and 53 per cent was 100-pound, 72-foot jointed rail with standard spiking and anchor pattern. There was a mix of 11-inch and 14-inch double-shouldered plates. Ballast was in poor condition. Traffic on the Aldersyde Subdivision in 2003 was 13.0 million gross tons (MGT), a 15 per cent increase since 2001, with 7 per cent unit train traffic. Rail defects per 100 miles tested decreased from 19.69 in 1999 to 11.42 in 2002, but increased to 16.52 in 2003.
R03E0092 (15 October 2003), Derailment of 14 Cars on CPR Train 863-017 at Mile 40.4 of the Taber Subdivision
Derailed cars included six residue cars of molten sulphur and eight empty coal cars. Track speed was 40 mph with a 25 mph temporary slow order in place due to poor ballast conditions. The primary cause was determined to be a broken rail due to a 15-inch vertical split head, and head and web separation. The rail was 1953 Dominion 66-foot jointed, 100-pound head free on tangent track relaid22 in the 1980s. The rail was ultrasonically tested one week before the accident. The defect was detected, but misinterpreted by the operator.
Rail on the Taber Subdivision was 100-pound and 115-pound jointed rail with standard anchoring and spiking. Ten-inch single-shouldered plates were used on rail under 100 pounds, and 14-inch double-shouldered plates were used on rail under 115 pounds. Ballast grade was fair to good on the east end of the subdivision and poor on the west end of the subdivision. Approximately 17 miles of CWR and 48 miles of plates were scheduled for installation in 2004. In addition, 31.4 miles of CWR were scheduled for installation in 2005 and 50 miles in 2006.
Traffic on the Taber Subdivision in 2003 was 15.7 MGT, a 43 per cent increase since 1999, with 80 per cent unit train traffic, transporting mainly bulk commodities such as coal, grain, sulphur, and potash. Rail defects remained relatively stable between 1999 (30.46 per 100 miles tested) and 2001 (30.75), decreased in 2002 (20.40) then increased in 2003 (39.44).
R03C0101 (24 October 2003), Derailment of 16 Cars on CPR Train 269-21 at Mile 10.75 of the Moyie Subdivision
Track speed through the area was 25 mph; the train was travelling at 27 mph. The weather was clear and the temperature was 9ºC. Derailed cars included one residue non-dangerous commodity tank car and one residue tank car that last contained sodium hydroxide. There was no loss of product from the tank cars. The primary cause of the derailment was a break in the high rail within the body of a six-degree left-hand curve due to a transverse detail fracture extending from the gauge corner of the high rail. The rail was 136-pound RE CWR manufactured by Algoma between 1980 and 1985. The last ultrasonic test before the derailment was on September 19, with no defects noted in the area. In the area of the POD, the rail flaw detector car showed an intermittent response typical of poor rail head surface condition, and no further action was taken by the rail test operator.
Rail on the Moyie Subdivision was a combination of 100-pound, 130-pound, 132-pound, and 136-pound rail with CWR on most curves and jointed rail on tangent track. Standard anchoring was used with double-shouldered plates and five spikes per plate on most curves, and single-shouldered plates and two spikes per plate on tangent track. Ballast was fair to poor. Approximately nine miles of rail were relaid between 2001 and 2004. Two miles of relay rail were planned for 2005 and 2006. Traffic on the Moyie Subdivision in 2003 was 16.0 MGT, a 33 per cent increase since 1999 with 26 per cent unit train traffic. Rail defects per 100 miles tested decreased from 17.61 in 1999 to 9.15 in 2001, increased to 26.76 in 2002, and then decreased to 20.13 in 2003.
R04E0001 (01 January 2004), Derailment of 28 Loaded Grain Cars on Canadian National (CN) Train A44351-01 at Mile 58.90 of the Camrose Subdivision
The northbound train was proceeding at 40 mph, slowing for a 25 mph permanent slow order between Mile 49.2 and Mile 58.4. The primary cause of the derailment was a broken rail in a joint on tangent track. The rail break was likely due to a bolt hole crack. The rail was 1949 Algoma 100-pound, 39-foot jointed (four bolt joints) rail with a 7 mm head loss. Ties were No. 1 hardwood in good condition, 14-inch double-shouldered tie plates with five spikes per plate, and anchors boxed every second tie. Ballast was crushed rock in fair-to-good condition.
The rail was 100 pounds of primarily CWR with the remaining rail 39-foot jointed, anchored every second tie. Ties were softwood except for hardwood on curves greater than four degrees with 11-inch double-shouldered plates and 14-inch double-shouldered plates on some curves, two spikes per plate with pin spiking on higher-degree curves. There were 20 to 30 per cent defective ties on average. Ballast was crushed rock in good condition. Over 16 miles of partly worn CWR had been installed and 15 200 electric flash butt welds done since 2001 to eliminate jointed rail. A total of 14 000 anchors, 3600 ties, 6000 spikes, and 4.52 miles of gauging were done, and 2600 cubic yards of ballast were placed. Train traffic in 2003 was 10.5 MGT, which was a 40 per cent increase since 2001. There was 21 per cent unit train traffic, mainly northbound sulphur and grain.
R04C0002 (05 January 2004), Derailment of 15 Cars on CPR Train 266-02 at Mile 76.4 of the Crowsnest Subdivision
Track speed was 35 mph and the train was travelling at 30 mph. Temperature at the time was -31ºC. All derailed cars were empty except for one residue liquefied petroleum gas tank car and one loaded phosphoric acid car. The primary cause of the derailment was a broken high rail in transition between five- and six-degree curves. Eleven pieces were recovered, and TSB examination determined that there were transverse defects in 12 of the 14 fractures, all in the gauge corner of the rail head, varying in size from 5 to 50 per cent of the cross-sectional head area. The last ultrasonic test, which had been done 03 October 2003, indicated a possible transverse defect near the POD, but the rail ultrasonic operator decided that the defect was less than 10 per cent and took no action because the rail surface was poor (significant checking and shelling). Rail was 1982 Algoma 115-pound partly worn CWR cascaded from the CPR main line in northern Ontario.
Rail was 100-pound jointed from Mile 7.9 to Mile 10.3, with single-shouldered plates. The remainder was 115-, 132-, and 136-pound CWR with 14-inch double-shouldered plates, except for 11-inch double-shouldered between Mile 48 and Mile 77. Anchoring and spiking patterns were standard. The ballast was rated as in good condition. Traffic in 2003 was 20.1 MGT, a 53 per cent increase since 1999, with 58 per cent unit train traffic. Rail defects per 100 miles tested increased from 2.14 in 2000 to 11.79 in 2002, levelling off to 11.53 in 2003.
R04C0014 (26 January 2004), Derailment of 11 Intermodal Service Cars on Southward CPR Train 104-26 at Mile 46.1 of the Red Deer Subdivision near Didsbury, Alberta
Permissible track speed was 55 mph and the train was travelling at 21.7 mph. The weather was clear at -29ºC, and a 35 mph cold weather slow order was in effect at the time. The primary cause of the derailment was broken rail/joint bars in the west rail. Fatigue cracks had developed from bolt holes in the south rail end of the joint. Well-developed fatigue defects were present on the fracture surfaces of both joint bars. Poor joint inspection and maintenance were contributing factors in this derailment. Rail was 1983 Algoma 115-pound CWR on tangent track with six-hole joint bars. The last ultrasonic test, 10 November 2003, identified a defective plant weld immediately north of the POD (not considered causal).
Rail on the Red Deer Subdivision is mainly 100-pound jointed with some 115-pound CWR. Overall traffic on the Red Deer Subdivision varied little between 2000 (25.0 MGT) and 2003 (26.4 MGT) with 14 per cent to 20 per cent bulk traffic.
R04C0031 (22 February 2004), Derailment of 22 Intermodal Platforms on Westbound CN Train Q11531-19 at Mile 37.21 of the Oyen Subdivision
Track speed was 40 mph and the train was travelling at 34 mph. Weather was clear and calm, at -6ºC. The primary cause of the derailment was a broken rail due to a vertical split head in a joint near a crossing. Rail was 1956 RA Dominion 100-pound, 78-foot jointed rail (four bolt joints) on tangent track. No rail defects were recorded in the area on the last previous ultrasonic rail test done on 17 June 2003.
Oyen Subdivision traffic in 2003 was 5.1 MGT, with 70 per cent intermodal and 30 per cent other freight, mainly grain. Maximum loading permitted on the Oyen Subdivision is 268 000 pounds.
R04E0027 (04 March 2004), Derailment of 20 Cars on Westbound CPR Train 575-03 at Mile 86.03 of the Red Deer Subdivision near Penhold, Alberta
Derailed cars included five residue cars of anhydrous ammonia, two residue cars of propylene and one residue car of sodium aluminate. The weather was clear and calm with a temperature of -18ºC. At the time of the derailment, the train was travelling at 39.2 mph. The posted subdivision speed at the POD was 45 mph; however, there was a slow speed order of 40 mph in effect in the area due to excess cross-level variation (not considered causal). The last rail flaw detector test was conducted between Mile 67.3 and Mile 95.6 on 13 February 2004, with no defects found. The train derailed as it passed over a rail joint in tangent track that had broken and separated. Two joints at both ends of a buffer bar were involved. All joint bars failed at their approximate middles with the fracture surfaces of the bars showing pre-existing fatigue fractures extending from the top fishing surfaces. The joint bars were weakened by these fatigue defects due to the poorly supported and unsecured condition of the joint and adjacent rails.
Selection of Canadian Pacific Railway Subdivisions
Those Canadian Pacific Railway (CPR) subdivisions not having an annual tonnage greater than 10 million gross tons (MGT) and a majority of rail weight under 130 pounds, according to data provided by CPR, were excluded from the final sample. The Hardisty, Wilkie, Estevan, and Sutherland subdivisions were excluded due to low MGT. The Cranbrook, Moyie, and Nelson subdivisions were excluded because a majority of the rail weighed more than 115 pounds. The Crowsnest Subdivision was also excluded because nearly all bulk traffic was borne by 132- or 136-pound rail. Although only 26 per cent of Crowsnest Subdivision rail is over 115 pounds, that heavy rail is entirely located between Mile 77.2 and Mile 101.1, where it bears nearly all of the bulk unit train traffic on that subdivision. The bulk coal cars travel south from the open-pit mines of the Elk Valley coalfield, then west and north through the Cranbrook Subdivision and on to the port facility of Roberts Bank on the west coast, so that the lighter rail located east of the open-pit coal mines of the Crowsnest Pass region bears very little of the bulk unit train traffic.
The following variables were averaged across 2002 and 2003:
- Overall tonnage - annual MGT;
- Bulk unit train tonnage - derived by multiplying the percentage of bulk unit train traffic (supplied by the railway) by overall MGT;
- Rail defect rate - annual rail defect count per mile of track;
- Surface roughness index - supplied by CPR.
|Subdivision||Average MGT||Average Bulk MGT||Average Rail Defect Rate||Average SRI|
|Red Deer *||25.70||3.64||0.48||55.00|
|Sutherland (Lanigan to Saskatoon)||9.40||5.90|
* denotes subdivision selected for statistical analysis
Rail defect rates and surface roughness index values are reported only for those subdivisions that met the selection criteria.
Railways rely heavily on testing rail for defects. The testing methodology used by all rail testing contractors is basically the same. The only differences are data processing speed, presentation of information, vehicle setup, and roller search unit (RSU) carriage construction. Over the years, Sperry Rail Service has developed and used RSUs that combine different transducer angles to achieve the best inspection possible. Fluid-filled wheels are used to house and couple the transducers to the rail. A liquid couplant consisting of a thin film of water mixed with glycol or calcium facilitates the transmission of ultrasonic energy from the transducers into the rail.
In the A-scan system, there are two wheels with nine transducers per rail-five transducers in one wheel and four in the other. Each rail has nine transducers: one zero-degree or vertical-looking probe, one forward-looking and one rear-looking transducer nominally aligned at 45 degrees (actually at 37 degrees), and six 70-degree probes. In the newer B-scan system, two additional "side-looking" modified 70-degree probes look at each rail head at a lateral angle for vertical separations for a total of 11 transducers on each rail. These arrays of probes result in a test of all the rail cross-section with the exception of the outside base edges. Because the B-scan ultrasonic testing technology permits a greater volume of rail to be tested and smaller defects to be detected, flaw detection is improved by approximately 50 per cent.
At Sperry Rail Service, there are two primary inspection units: a rail-bound vehicle that uses both ultrasonic and electromagnetic (induction) technologies to identify defects, and an ultrasonic-equipped hi-rail truck. In the past, induction equipment has been too large for hi-rail vehicles, but Sperry Rail Service has recently developed an induction system that operates on a hi-rail platform. The vehicles will test rail between 6.5 and 13 mph, and vehicles operating at higher speeds are under development.
The data from the inspection equipment are fed to the operator inside the car and visually presented on monitors. Six channels display the ultrasonic and induction signals and where exceptions occur relative to track features such as joints and crossings. If the operator considers an indication suspect, the test vehicle is stopped and backs up to the point of examination. The operator gets out and hand tests the rail with an ultrasonic test set mounted on the rear of the car. If a defect is confirmed, it is marked and a rail work crew following the Sperry Rail Service car changes the rail or otherwise protects it.
Selecting an appropriate frequency for rail testing is a complex task involving many different factors including temperature, traffic density, rail sections, and accumulated tonnage. The Railway Track Safety Rules (TSR) specify an annual test of rail for internal defects of all track in classes 4 through 6 over which the annual gross tonnage is 25 million tons or more and in Class 3 track over which passenger trains operate. Both Canadian National (CN) and Canadian Pacific Railway (CPR) recognize the value of frequent testing and exceed this requirement, particularly during the colder winter months when rail is more brittle and susceptible to defect growth.
The number and types of rail defects form a database used by the railways in the development of rail replacement programs and to give an overall sense of the defect history of a subdivision. CN's rail defect severity program calculates total rail defect severity or rail defect indices (RDI) across a subdivision. The program assigns a severity value for each defect based on the type of defect. Fatigue defects such as vertical split head, head and web separation, transverse defect, and horizontal split head have higher values than defects due to wear such as battered end, curve wear, flowed rail, and shelly rail. The sum of all severities for a five-mile window is calculated and plotted on a rail severity plot. The plot allows for enhanced planning and prioritizing of rail replacement programs, which are then included in the railway's overall capital renewal plan where the requirement for rail competes with other corporate capital demands. Approved rail programs are nearly always less than what has been requested, resulting in local supervisors placing their allotment in the highest risk locations.
At CPR, defective rails are replaced or protected as required by its Standard Practice Circular (SPC) 27. According to SPC 09, Section 4.2, rail is replaced through a whole curve at wear limit A (wear limits for planning rail relay where there is evidence of fatigue), rather than C (maximum wear limits at which rail must be removed from track). Rail is considered to be fatigued when there is evidence of one rail defect of a fatigue type within the past 12 months or two rail defects within the past 24 months. CPR has no hard standard on the number of defects occurring in tangent track that would automatically trigger a change-out. This is done on a case-by-case basis, depending on the nature of the defects.
CPR's SPC 09, Section 8.0, provides rail replacement guidelines based on the TSR class of track. New or relay continuous welded rail (CWR) is the guideline for all tonnage classes of secondary main lines and above; however, the actual decision concerning the rail to be used may be influenced by availability of rail, costs, and future prospects of the line.
Sperry Rail Service has taken the following steps to ensure that operators are sufficiently trained to reliably identify rail defects:
- The company employs a training program in which an operator progresses from driver to assistant to chief, which lasts between one and three years including on-the-job training. Before proceeding to the next level, the operator receives 40 hours of formal training in ultrasonic testing and must demonstrate competence according to a standard recognized by the American Society for Nondestructive Testing (ASNT).
- Rail test results are monitored and any in-service failures occurring within 30 days of a test are investigated and successive inspections on a given track are compared to identify any defects missed. An operator who has not identified defects that were present is given feedback and/or remedial training.
- Although Sperry Rail Service seeks to maximize miles tested each day, the chief is responsible for the conduct of the test and the pace of the task. Since rail testing contracts are based upon hours worked, not miles tested, operators can take the time required for hand testing and visual inspections, and can stop the car to redo a section if deemed necessary.
Sperry Rail Service, CN, and CPR have adopted the American Railway Engineering and Maintenance of Way Association (AREMA) Recommended Minimum Performance Guideline for Rail Testing. The performance guideline specifies the minimum acceptable performance in terms of the percentage (reliability ratio) of actual in-track defects that can be expected to be located in a single test by a test car maintained in reasonable condition and operated by an experienced operator in service over a typical mix of track conditions. Since 100 per cent accuracy in testing is not within the capabilities of current technology and equipment, the performance guideline also specifies the number of valid defects in track that are not reported or are otherwise missed. For example, AREMA testing performance standards specify a reliability ratio of 75 per cent for bolt hole cracks 2 inch to 1 inch in length for Category I track. Detection of smaller cracks is not assured. Reliability ratios depend on size of defect and category of track. Category I track includes all main track with annual tonnage equal to or exceeding 3 million gross tons (MGT) per year, or with train speeds equal to or exceeding 40 mph. Category II track includes all sidings and track with annual tonnage less than 3 MGT per year, and with train speeds less than 40 mph.
Following a Transport Canada (TC) inspection of the Moyie Subdivision in October 2004, a TC Notice and Order was issued 29 October 2004 regarding high density or defective track ties, worn and defective rails, inadequate rail joint maintenance, and fouled and insufficient ballast. Both the Cranbrook and Moyie subdivisions were placed on special inspection status (more frequent and detailed TC inspections to be done).
A TC Notice and Order was issued 08 May 2003 regarding general poor tie conditions and high/broken fasteners on the latter portion of the subdivision, and increasing tonnage and heavier axle loads. Although some improvements were noted as a temporary measure, Canadian Pacific Railway (CPR) was advised on 29 October 2004 that the Notice would remain in effect due to poor rail joint maintenance, worn rail, inadequate turnout maintenance, and sub standard track conditions in Cranbrook Yard.
On 17 July 2002, TC inspected the track between Mile 55.69 and Mile 114.64. This inspection recorded fouled ballast conditions, defective tie clusters, tie and tie plate deterioration, ineffective anchoring, and general poor track conditions. TC wrote to CPR on 18 July 2002, requesting information on CPR's rail, tie and ballast program, both for work completed in 2001 and work planned for 2002. CPR was given 14 days to provide details of the corrective action it planned to take to address the track deficiencies identified during the July 17 inspection. CPR responded on 08 August 2002, outlining the immediate corrective action taken. However, there was no supplementary information regarding the long-term maintenance plans necessary to address the inspector's observations.
On 08 January 2003, another inspection was completed between Mile 32.5 and Mile 62.0. On 10 January 2003, TC identified concerns regarding the ongoing maintenance and accelerated track degradation due to the overall subdivision tonnage increases and increased car loading over the previous four years. TC requested that CPR provide it with details by 30 April 2003 of its plans to maintain the infrastructure of the Taber Subdivision to safely handle anticipated rail traffic. CPR responded on 28 April 2003, indicating that, for 2003, the maintenance plans on the Taber Subdivision would include relay rail installation, turnout upgrades, and broken tie plate replacement. In addition, CPR provided TC with its multi-year maintenance plan for 2004 to 2008. TC reviewed this information and expressed concerns regarding the tie program and the plan to address the sub-standard ballast conditions. CPR was requested to review TC's concerns and provide a follow-up.
On 22 September 2003, CPR advised TC that it was limiting train speed on the subdivision until it had the infrastructure upgraded with better rail, fastenings, ballast, and, where necessary, ties. CPR also indicated that TC's other earlier concerns could be addressed through appropriate revisions to the capital plan. There was no further information on what revisions were being contemplated for the capital plan.
|AAR||Association of American Railroads|
|AREMA||American Railway Engineering and Maintenance of Way Association|
|ASNT||American Society for Nondestructive Testing|
|CPR||Canadian Pacific Railway|
|CWR||continuous welded rail|
|E||annual express tonnage|
|F||annual freight tonnage|
|FRA||Federal Railroad Administration|
|HAL||heavy axle loading|
|MGT||million gross tons|
|mph||miles per hour|
|NTSB||National Transportation Safety Board|
|p||statistical significance value indicating the probability that the relationship is due to chance|
|P||annual passenger tonnage|
|POD||point of derailment|
|r||correlation coefficient representing the linear relationship between two variables|
|r2||coefficient of determination representing the strength or magnitude of the relationship between two variables|
|RAC||Railway Association of Canada|
|RSA||Railway Safety Act|
|RDI||rail defect indices|
|RSU||roller search unit|
|SII||safety issues investigation|
|SMS||safety management system|
|Se||speed factor for express trains based on train speed|
|Sf||speed factor for freight trains based on train speed|
|Sp||speed factor for passenger trains based on train speed|
|SPC||standard practice circular|
|SRI||surface roughness index|
|STR||speed tonnage rating|
|TQI||Track Quality Index|
|TSB||Transportation Safety Board of Canada|
|TSR||Railway Track Safety Rules|
|TTCI||Transportation Technology Center Inc.|
|WILD||wheel impact load detector|
|≥||equal to and greater than|
|n||root number of data points|
- For the purpose of this investigation, secondary main lines are non-signalled.
- See Glossary at Appendix E for all abbreviations and acronyms.
- Moyie, Cranbrook, Crowsnest, Taber, and Weyburn subdivisions
- Macleod and Aldersyde subdivisions
- Blackfoot, Vegreville, Brazeau, Camrose, Sangudo, and Three Hills subdivisions
- Elastic recovery refers to the track's ability to return to its original shape after being loaded and unloaded.
- Heavy Axle Loads Needs Assessment for the American Short Line and Regional Railroad Association, Zeta-Tech Associates, May 2000.
- Upgrading Short Line and Regional Railways Infrastructure to Accommodate Heavier Axle Loads, IBI Group, 2002.
- Surface roughness index (SRI) is an average of the number of occurrences of surface defects; that is, track geometry-related defects. Comparison of SRI values between runs gives an indication of track condition over time, with a lower number indicating better track.
- A t-test is a statistical technique for determining if two samples are significantly different.
- T.C. Krehbiel (2003), "Correlation coefficient rule of thumb," submitted to The Decision Science Journal of Innovative Education (Dr. Krehbiel is Professor of Decision Sciences and Management Information Systems, Richard T. Farmer School of Business, Miami University). The article is a rigorous proof that the critical correlation (that is, the lowest statistically significant correlation) is given by 2 /n, which is only possible if n ≥ 5.
- CN's 286 000-pound loading ranged from 5.2 per cent on the Blackfoot Subdivision to 15.7 per cent on the Three Hills Subdivision. CPR's 286 000-pound loading ranged from less than one per cent on the Crowsnest, Aldersyde, and Macleod subdivisions to 4.19 per cent on the Taber Subdivision. However, the total 286 000-pound tonnage was lower on CN.
- R03E0092 (15 October 2003, Mile 40.4, Taber Subdivision) Some of the occurrences referenced in this report have been the subject of a preliminary TSB investigation only. However, summary reports are available upon request.
- R04C0002, R03C0101, R03E0091
- AREMA Committee 4, Sub Committee 9 presentation to the AREMA annual convention in September 2003 in Chicago, Illinois.
- As the rail wears with tonnage over the surface, non-conformal wheel-to-rail contact geometry creates excessive stresses that cause rail surface plastic flow and surface fatigue (spalling, shelling, and head checks) and that mask other internal defects. As rail wears, stresses in the rail come into contact with internal inclusions and act as a nucleus for various types of defect growth.
- R01W0025, R01W0032, R04E0001, R01E0017
- R03T0064, R04C0014, R04T0027, R04W0064, R04E0027, R04T0015, R04T0016, R04C0031, R00E0126
- A joint bar inspection system currently under development and testing will enable detection of cracked joint bars at speeds up to 50 mph.
- Martensite is hardened brittle steel.
- Chamfering is a process by which a bevelled surface is added to the bolt hole as it emerges from the rail web.
- The term "relay" refers to the practice of the re-laying used continuous welded rail with residual service life that has been taken from principal main track.
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