With the fifth phase of HAL research due for completion next year, it is clear that substantial benefits accrue from heavy axleload operation. Cumulative savings from the use of HAL techniques and equipment in North America during the 1990s are of major significance

Semih Kalay is Assistant Vice President, Research & Development, at Transportation Technology Center, Inc. Carl Martland is Senior Research Associate at the Massachusetts Institute of Technology

NEXT YEAR will see the fifth phase of the Association of American Railroads' HAL (Heavy Axleload) test programme draw to a close. HAL has been the main component of extensive research carried out in the last 15 years by Transportation Technology Center Inc, an AAR subsidiary, into the safety, technical and economic issues arising from an increase in axleloads. The programme has been jointly funded by the AAR and the US Federal Railroad Administration with significant co-operation from railroads and suppliers.

It is now widely accepted that increasing the capacity and gross weight of freight cars can improve freight train productivity. Savings arise because fewer train crews are needed to haul a given tonnage, and if the ratio of net to gross tonnage can be increased, more savings can be achieved in fuel, track and equipment costs. Another benefit is that fewer trains means less delay at passing loops on single track lines. On the other hand, these benefits are offset by an increase in track and bridge costs.

More than 1000 MGT of HAL traffic have been accumulated at the FRA's Facility for Accelerated Service Testing (FAST) in Pueblo, Colorado. After each test phase was completed, an economic analysis compared the costs and benefits of moving to heavier cars. The effects of HAL operations on track costs were estimated using deterioration models calibrated to the FAST results, information from other research, and experience.

Results show that, in general, heavier axleloads will increase track and facility costs, but reduce operating and equipment costs. As track costs are much less than operating plus equipment costs, HAL operations can be worthwhile even if the percentage increase in track costs is far greater than the percentage reduction in operating plus equipment costs.


Over the past decade or more, a shift in the mix of North American traffic towards bulk commodity, unit train operations such as coal and grain has raised the question of whether the railroads should increase loading capacity from 100 to 125 ton cars.

In 1986 the AAR began a study to define the optimum axleload for economic and safe operations. The steering committees asked for full-scale tests of the effects of 125 ton cars on track degradation rates and increased maintenance costs. Prior studies indicated that a 13 to 15% reduction in operating costs compared with 100 ton cars was possible, despite potentially significant increases in track maintenance costs. Although the best available track degradation models and data for 35 tonne axleloads were used, this was insufficient to provide definitive results, and the extrapolation required to predict the effects of 125 ton cars suggested that more work was needed.

In 1988 the FAST programme replaced a train of 100 ton cars (29 tonne axleloads) with cars of 125 ton capacity to conduct controlled tests and evaluations of heavy axleload traffic. A fleet of high-sided gondolas, covered hoppers, and tank cars was each loaded to a gross weight of 142 tonnes.

Normally, the consist includes about 75 HAL cars and is hauled by four or five four-axle locomotives at a steady 65 km/h over the 4·3 km High Tonnage Loop at TTCI. On a typical day the train accumulates 1 MGT and around 435 km,with the train running in both directions on the loop to equalise wheel wear.

Five test phases

The performance of conventional track materials under HAL traffic was measured in 1988-90 during Phase I of the test programme, when 160 MGT of traffic was accumulated (RG 6.91 p373). This study concluded that for the first 160 MGT of accumulated traffic at FAST, for the type and condition of conventional North American track tested, no catastrophic failure occurred. But stresses and deterioration rates increased under 125 ton cars, as did the ensuing maintenance requirements.

The most significant problems encountered were:

  • Field welds and joints, with field weld life falling by 50% under HAL traffic;
  • Standard rail (300Brinell hardness and less) in sharp curves suffered from accelerated wear, and surface fatigue required frequent grinding on rail subject to corrugations and metal flow;
  • The standard North American test turnout with standard components required excessive maintenance and was removed from track after 100 MGT owing to component failure. Routine maintenance increased more than 50%.

In Phase II, additional tests were conducted using premium track components and improved maintenance techniques. Phase II analysis showed that the effects from HAL on the track structure were lower than predicted in Phase I, thanks to better track components and improved understanding of deterioration rates. The analysis highlighted the importance of good components and, especially on poorer quality track, the need to budget for increased maintenance on lines with significant HAL traffic.

In Phase III, another series of tests was completed using 125 ton cars mounted on trucks with improved suspension under lubricated rail conditions. The economic analysis concluded that the extra costs associated with improved suspension trucks could indeed be justified by reductions in expenditure for track, equipment maintenance, and fuel.

In Phase IV, the effects of dry rail operations with improved suspension trucks were quantified on track performance and fuel consumption. During the current Phase V, tests are under way to determine the HAL effects on new track components using newer generation three-piece trucks in current use in North America.

Economic analysis methodology

The ultimate objective of the HAL programme is to provide guidance to the North American railroad industry about whether to increase axleloads, and to determine the most economic payload consistent with safety. This can only be done if the physical test results can be translated into the costs of operating cars with heavier axleloads. To evaluate the economics of HAL operations, life-cycle costing was used to relate the technical data from FAST tests to costs.

The effects of HAL operations on track costs were estimated by using deterioration models calibrated to the FAST results, information from other research, and experience. The track models were used to estimate track costs for 100 ton base case cars; 110 ton cars, and 125 ton cars.

Operating costs were estimated by identifying specific consists that could be used for unit coal trains on a typical 30 MGT line in the east and a typical 80 MGT line in the west. The unit costs, track components, maintenance practices, and track deterioration parameters were first developed for the Phase I Economic Analysis under the direction of the AAR HAL Research Committee.

Case studies of actual coal lines were also conducted in Phase I in co-operation with an eastern and a western railroad to validate the methodology. The case studies of the eastern and western coal lines were updated at the end of Phase II and Phase III, taking into account changes in track components and unit costs, as well as the most recent knowledge of the effects of HAL operations on track structures. Further case studies covered a broader set of possible car designs and operating conditions.

The research demonstrated conclusively that addressing the key problems would make HAL operations more attractive. For track, there are five areas where rising costs act as a constraint to axleloads:

  • age, type and condition of bridges;
  • rail defects, especially sections with poor quality rail;
  • sections with poor ballast or subgrade conditions;
  • track that needs extensive routine maintenance, for example turnouts, and other special track;
  • the economic needs of short lines against those of larger railroads.

Premium track components, better maintenance procedures, and improved suspension trucks tend to reduce the HAL effects on track maintenance costs. Hence there is a case for continuing with technical innovation and upgrading infrastructure, especially strengthening and replacing older bridges.

Benefits accrue for all traffic

Track structure improvements that cut the cost of HAL operations also tend to reduce the costs of the base case (100 ton car) operations. As the HAL studies progressed from Phase I to Phase III, considerable improvements in track and vehicle components reduced the costs of the base case as well as the HAL options. Table I lists the base case track costs for eastern and western coal lines for the three phases.

Using better components in Phase II gave a 7 to 8% reduction in base case costs for track, with most of the improvements coming in maintenance rather than capital costs. In Phase III, the use of improved suspension trucks provided a further 8 to 10% improvement in track costs, with equivalent cost savings in both maintenance and capital costs.

Track and bridge costs up

Results from Phase II are the best to use in estimating the costs and savings from implementing HAL operations as they consider HAL loads in cars with standard trucks. Although the savings in Phase III appear to justify the use of cars with better suspension trucks, they have yet to be introduced in significant quantities on coal trains.

Results from Phase II (Table II) show that HAL operations have a much greater effect on maintenance than on capital costs, which are more important in terms of life-cycle cost. Total track costs were predicted to rise by 5 to 10% under 110 ton cars and by 15 to 18% under 125 ton cars.

Bridge costs, which were included as a separate category, were predicted to rise faster than track costs. While the predicted increases for bridges were extremely high, bridge costs were only 10 to 15% of track costs in the base case, so they did not dominate the analysis.

Crew and fuel costs down

For operations, the key source of benefits from HAL is the ability to operate with a higher net tonnage per train. Constraints on train length and improvements in the ratio of net-to-gross tonnage therefore tend to increase the operating benefits.

Table III lists the basic HAL economics. Although infrastructure costs rise substantially, operating costs fall. As operating costs are so much higher than infrastructure costs, total costs are lower. In these examples, the operating costs actually decline more for the 110 ton car case than for the 125 ton car case, primarily because of the net-to-tare benefits of the particular 110 ton car used. In every case, the 110 ton car was found to be superior to the 125 ton car.

Both costs and benefits are highly route and site specific. The most promising opportunities are for high density, unit train operations over good track, especially where train lengths and line capacity are limited. The situations that are least likely to be justified on a cost-benefit basis are HAL operations over light density lines where the track structure is weak and there are no problems with train length or line capacity.

Calculating the benefits

The magnitude of benefits from HAL operations depends on the extent to which HAL loads are operated. A recent retrospective industry analysis suggests that the railroads have in fact followed the recommendations of the HAL Economic studies:

  • The North American industry adopted the 110 ton car as the HAL standard, as recommended after Phases I, II, and III. When room was available in existing equipment, railroads increased loading limits very soon after the Phase I study. Railroads then upgraded their fleets through attrition, replacing older cars with 110 ton cars.
  • The extensive studies of possible HAL effects on track were critical in identifying and avoiding potential problems associated with weak elements in the track structure.
  • The actual effects have generally been consistent with the assumptions of the HAL economic analysis in that no significant problems in implementation have yet been identified.

The operating benefits are very substantial. The annual net benefit from HAL operations using 110 ton cars is estimated to be hundreds of millions of dollars per year if all traffic moves in such cars.

More savings to come

In fact, the transition to 110 ton cars is still under way, with a quarter to a half of the traffic on high-density lines moving in HAL cars. Using aggregate data for coal tonnage and car loadings, we find that the average carload of coal increased from 96·3 tons (87·3 tonnes) in 1987 to 106·6 tons (96·7 tonnes) in 1998. This increase includes the effects of the shift to lighter aluminum cars as well as the increase in axleloads.

To isolate the axleload effects, we used data from three wayside load stations to estimate the percentage of loaded cars with HAL loads. At a typical detector on a coal line in the west, 38% of cars were HAL loads; this figure is the percentage of cars for which the wheel loads indicated a gross vehicle weight of more than 139 tons (126 tonnes). As the HAL loads carry more traffic, the percentage of tonnage was somewhat higher, namely 42%. At two typical detectors in the east, an average of 11% of the cars and 13% of tons were estimated to be HAL loads. However, there is some of each type of track in the east and in the west. Therefore, the average rate of implementation was 38·7% in the west (15285 km of track modelled as the 80 MGT line and 38938 km as the 30 MGT line) and 27·1% in the east (with 1609 km modelled as the 80 MGT line and 35398 km as the 30 MGT line).

For this level of implementation, the annual benefits are estimated to be in the range of $250m to $500m. If we look at the cumulative savings during the 1990s, assuming a steady rate of implementation, then the total saving to date from HAL operations in North America is on the order of $1bn to $2bn.


In this article we have used the following terms:

100 ton car: payload of 100 short tons, gross weight generally around 118 tonnes, axleload approximately 30 tonnes

110 ton car: payload of 110 short tons, gross weight around 130 tonnes, axleload approximately 32·5 tonnes

125 ton car: payload of 125 short tons; gross weight generally around 140 tonnes; axleload approximately 35 tonnes

TABLE: Five phases of the HAL research programme

Phase Date Tonnage Description

I 1988-90 160 MGT Initial 35-tonne axleload testing, standard trucks and standard track

II 1990-95 300 MGT Standard trucks, premium track components

III 1995-98 425 MGT Improved suspension trucks, premium track components

IV 1999 55 MGT Improved suspension trucks, premium track components, no rail lubrication

V 1999-2002 415 MGT Standard trucks, premium track (projected) components, (predominately) standard rail lubrication with other lubrication practices tested, periods of under- balance speed operations (planned)

TABLE: Table I. Comparison of base case track costs for HAL Phases I, II, and III

West I West II West III East I East II East III

Maintenance 100% 92·4% 75·7% 100% 82·2% 75·1%

Capital 100% 91·4% 88.6% 100% 97·2% 86·3%

Total: 100% 91·7% 85·1% 100% 93·2% 83·3%

TABLE: Table II. Infrastructure costs under HAL operations, Phase II results

West 100 West 110 West 125 East 100 East 110 East 125

Track maintenance 100% 111·3% 132·7% 100% 122·6% 147·5%

Capital 100% 102·6% 108·6% 100% 106·5% 110·0%

Total 100% 105·0% 115·1% 100% 110·3% 118·8%

Bridges 100% 112·7% 156·9% 100% 114·0% 137·7%

TABLE: Table III. Operating costs with HAL equipment, Phase II results

West 100 West 110 West 125 East 100 East 110 East 125 Baseline Baseline

Track 100% 105·0% 115·1% 100% 110·3% 118·8%

Bridges 100% 112·7% 156·9% 100% 114·0% 137·7%

Operations 100% 90·4% 93·8% 100% 91·1% 95·3%

Total 100% 92·6% 97·5% 100% 94·0% 99·6%

CAPTION: Canadian Pacific Railway has been working steadily to increase the productivity of its assets with higher payloads per train. A pair of General Electric AC4400s hauls empties back to the mine in western Canada

CAPTION: Track costs will rise when HAL operations are introduced, making it important to use high quality track with low maintenance components. This Union Pacific train is about to traverse moving frog points installed on the Hastings bypass between North Platte and Kansas City

Financial benefits from heavier axleloads

The Heavy Axle Load (HAL) programme at the Transportation Technology Center in Colorado has carried out research into the technical, economic and safety issues raised by increasing the standard axleload on US railways. An economic analysis compared the costs and benefits of increasing permitted axleloads, and found that as track costs are much smaller than the combined operating and equipment costs, HAL operations could be financially beneficial. Savings for US railroads over the last decade are estimated to lie between $1bn and $2bn.

Des avantages financiers grâce à des charges à l'essieu plus élevées

Le programme HAL (pour Heavy Axle Load, charge à l'essieu élevée) du Transportation Technology Center au Colorado a consisté à mener des recherches sur les questions techniques, économiques et relatives à la sécurité, soulevées par l'augmentation des normes de charge à l'essieu sur les réseaux des Etats-Unis. Une analyse économique a comparé les coûts et bénéfices d'un accroissement autorisé des charges à l'essieu et a fait apparaître que les coûts de la voie sont bien moindres que les coûts combinés d'exploitation et d'équipement, et que l'exploitation faisant appel aux charges à l'essieu importantes pourrait donc se révéler financièrement bénéficiaire. Au cours de la dernière décennie, les économies réalisées par les réseaux des Etats-Unis sont estimés entre un et deux milliards de dollars

Finanzielle Vorteile durch h?€?here Achslasten

Das Heavy Axle Load (HAL, Hohe Achslasten) Programm des Transportation Technology Center in Colorado führte umfangreiche Forschungen zu technischen, wirtschaftlichen und sicherheitsrelevanten Themen, welche mit einer Erh?€?hung der Achslasten auf den Nordamerikanischen Bahnen verbunden sind. Eine wirtschaftliche Analyse, in welcher die Kosten und Nutzen einer Erh?€?hung der maximal zulässigen Achslast verglichen wurde, zeigte, daß die Kosten für den Oberbau viel geringer sind als die kombinierten Betriebs- und Betriebsmittel-Kosten, dass h?€?here Achslasten tatsächlich zu finanziellen Vorteilen führen. Die dadurch erzielten Einsparungen für die US-Bahnen über die letzten 10 Jahre werden auf 1 bis 2 Milliarden US-Dollar geschätzt

Beneficios económicos de cargas por eje m? s elevadas

El programa Heavy Axle Load (HAL) del Transportation Technology Center en Colorado ha llevado a cabo un estudio sobre temas técnicos, económicos y de seguridad suscitados por el incremento del carga por eje est? ndar de los ferrocarriles norteamericanos. Un an? lisis económico comparó los costes y los beneficios del incremento de las cargas por eje permitidas, y observó que como los costes de las vías son mucho m? s pequeños que la combinación de los costes de explotación y de equipo, las operaciones HAL podrían ser económicamente beneficiosas. Se estima que los ahorros para los ferrocarriles norteamericanos durante la última década est? n aproximadamente en los mil millones y dos mil millones de dólares