Many harness racing tracks have been, and continue to be, built with avoidable errors in designing curve radii, crossfall, drainage, and racing surfaces.
The consequences of poor racetrack geometry and surface construction, including equine lameness and a general financial loss to the industry, are reviewed in this report. Brief guidelines for the construction of tracks of acceptable geometry are given, and the comparative advantages in both enhanced speed and reduced injury rates are discussed. In order to facilitate more valid track comparisons, a universal track rating system is proposed, and the advantages of such a system for trainers, drivers, officials, and the industry generally, are explored.
The author wishes to acknowledge David Evans, who assisted with the preparation of this article.
POORLY designed harness racetracks have long been identified as a major cause of economic loss to racing clubs, as well as of avoidable injury to horses. The record shows that many clubs have been poorly served by track designers, with some tracks having to be ripped up weeks or months after completion to correct avoidable errors in the original work. The harness racing industry pays a high price for these tracks in the form of corrective costs, loss of animals through avoidable injury, lower ex- port prices, and meetings needlessly lost through wet weather:
"The selective breeding of racehorses for speed over several generations has resulted in the production of horses of high performance potential in what is now almost an industrial enterprise, involving considerable financial investment. Many horses are not capable of withstanding the severe stress to which they are necessarily subjected during training and racing, and hence develop locomotory lesions of varying severity at a relatively young age. The increased speed and frequency of modern racing demand high standards of training and shoeing and optimum design and maintenance of racetracks. Recent investigations have shown a relationship between defects in track design and locomotory disturbances predisposing to lameness." -Fredricson and Alm (1972)
Since the above words were written in the early 1970s, there has been a further significant increase in the speed of the Standardbred, so much so that the rate of improvement has led some commentators to foreshadow a time when harness racers equal or surpass the speed of thoroughbreds. Be that as it may, the fact remains that the inadequately banked tracks ubiquitous in most of the world extract an increasingly unacceptable price.
With the current critical shortage of available starters in many areas, it is folly to continue to permit injury-promoting and poorly drained tracks to be constructed, and yet that is exactly what has happened. The $17.6-million (U.S. dollars) redevelopment of Sydney, Australia's main metropolitan track, Harold Park (see Figure 1), is the most recent example of a track requiring major and expensive rework to correct avoidable errors in the original work.
| Track Circumference (meters) | Length of Straights (meters) | Raduis of Turns (meters) | Min. safe bank angle for 1:50 mile rate (degrees) | Optimum Angle (degrees> |
| 804.672 | 169.40 | 74.11 | 7.32 | 17.23 |
| 1,005.84 | 211.76 | 92.64 | 3.26 | 13.26 |
| 1,408.18 | 296.46 | 129.70 | 1.72* | 9.55 |
| 1,541.00 | 324.42 | 141.93 | 1.72* | 8.74 |
| 1,609.344 | 338.81 | 148.23 | 1.72* | 8.38 |
| 1,900.00 | 400.00 | 175.00 | 1.72* | 7.11 |
In their 1974 paper, Fredricson, et al., set forth a number of basic principles of track design derived largely from prior work in railroad track and highway construction.
The paper was part of a research program for racetrack improvement sponsored by Harness Horsemen International, U.S.A; Harness Tracks of America; United States Trotting Association; and the Canadian Trotting Association. The authors summarised their paper:
'To enable racehorses to maintain their gait, the design of racetracks must comply more closely with the principles of ergonomics and highway engineering, especially in respect of curve geometry. In future tracks of adequate length and straight/curve ratio, the curves have to be suitably banked to provide more suitable condition of motion. Also, transition curves between the semicircular curves and the straights will eliminate present day disturbances in gait symmetry at the entrance and especially the exit of the curves.
"Existing tracks can easily be improved by increased banking of the curves, incorporation of transition curves, and elimination of slopes in the straights. These measures may be expected to reduce the incidence of lameness and improve racing performance."
Essentially, Fredricson and Alm (1975) argued that the flat or "underbanked" turns common in harness racetracks caused significant and avoidable injuries to horses.
Several articles have supported the need for optimal banking of tracks. Dr. Hilary Clayton (1987) expressed the view that "the majority of tracks will continue to be oval in shape but it is highly recommended that short, narrow turns be abandoned in favour of wider, more sweeping turns, with the incorporation of transition curves.
"Short tracks, although they are convenient for spectators, tend to be harder on the horses. For example, a half-mile track with sharp turns requires such heavy banking of the curves that it becomes difficult to maintain since the top cushion tends to slide down toward the inside rail. Consequently, short tracks are usually underbanked."
And when tracks are underbanked, they tend to injure horses. Fredricson and Alm (1972) stated: 'With optimum track banking, the strain on the horse caused by the curves will be relatively small (limited to the increase in sensible weight resulting from centripetal force), provided that the radius of the curve is not too short, even at speeds within a range around the design speed, covering most race requirements.
"Underbanked curves have been shown to cause gait asymmetry, leading to abnormal stresses in fast-moving horses (Rooney, 1969; Fredricson, et al., 1975; Dalin, et al., 1973). There is no longer any justification for the heavy underbanking that exists today."
Clayton also supported the earlier work of Fredricson and Alm, writing, The curves of a racetrack should be designed in a similar manner (to good highway engineering practice) so that the horse has optimum conditions of motion at a predetermined speed ('the design speed). Under these circumstances, the limb axes will be perpendicular to the track, so that hooves land flat and avoid the mediolateral stresses that occur in underbanked turns."
We simply cannot have it both ways. Either the track design speed closely approximates the average racing speed of a horse on that track, or the horse is denied optimum conditions of motion."
Kemp's Engineering Handbook (1975 edition) has an excellent explanation of the purpose of transition turns, which may be paraphrased as follows: "The purpose of a transition curve is to achieve a gradual change of direction from the straight to the minimum radius of the curve in order to eliminate the sudden shock caused by the introduction of centripetal force. For any constant speed, the value of the centripetal force is proportional to the radial acceleration. A basic requirement of transition curves is that the rate of change of radial acceleration shall be constant throughout the curve and of such value that there is no discomfort to passengers travelling on the curve. If the rate of change of radial acceleration is to be constant, the radius of curvature at any point on the curve will be inversely proportional to the distance of that point from the start of the curve."
Transition turns have long been used on Australian tracks, and they have been used at the Red Mile in Lexington, Kentucky, and other tracks in the U.S. for more than a century.
Anecdotal evidence suggests that when the angle of lean relative to the track surface exceeds 10', the incidence of injury to horses can be expected to increase sharply. The harder the track surface, the sooner the onset of injury.
Notwithstanding the provision of optimum bank angles, the tighter the turn, the greater will be the load on the horse's legs for any given speed. The load is simply the horse's weight plus the centripetal force accelerating the horse towards the center of the turn.
At a 2:00.0 mile rate, for example, a horse of 500 kg weight would experience an extra load of 13.35 kgs on a turn of radius 70 meters. Given a radius of 120 meters (similar to the Red Mile track) at the same speed, the same horse would experience a load increase of only 7.79 kg, i.e., 5.56 kg less. Aside from the increased load during the turns, more turns must be negotiated per mile on the smaller tracks, thus exacerbating the disadvantage. The driver and sulky also experience greater load-induced drag on small tracks for the same reasons.
This is why-all other things being equal-big tracks will always be faster than small tracks. The centripetal force required to negotiate the bends on tracks has its exact equivalent in a gradient on a straight track such that, for any given velocity, we can readily determine the Equivalent Vertical Displacement (EVD) of such a straight track over its oval counterpart. Taking a velocity equivalent to a 1:50 mile rate, an optimum 1,609 meter oval will have an EVD of 13.98 meters, an optimum five-eighths-mile track 21.04 meters, and an optimum half-mile track 27.97 meters. Given a horse/sulky/driver combined weight of, say, 400 kilograms, the climb will cost the animal half a kilowatt for the mile equivalent, three-quarters of a five-eighths-mile equivalent, and a full kilowatt for the half-mile track equivalent.
1,400-meter tracks (approximately seven-eighths of a mile) represent what many authorities believe to be an optimal compromise among speed, safety, and maintenance on the one hand, and the need to have the field pass the spectators twice during a one-mile race, on the other.
In addition to the concepts of turn radii and bank angles is that of the track surface finishing technique, generally described as "cushion." A correctly engineered cushion softens the surface and may alleviate some of the injuries caused by underbanked turns, while improving results from even the best track geometry. Dr. Albert A. Gabel had this to say (Hoffman, 1985): "The real problem is with tracks being too hard. The track must be springy; it has to have resilience. The track has to be tuned to the frequency of the foot and then the horse will bounce off the track and that gives you speed. That's what they have done at Delaware, Ohio. About three or four weeks before the Little Brown jug, they go out there with road equipment, dig up the track eight inches (20 cms) deep. That works air into it. They level it precisely and get it smooth. As they get it packed down, there's air in it, and if you train a horse over the track you can hear the difference. The track sounds springy, and it is springy, and that's why they get speed (but not the injuries.)"
However, irrespective of the excellence or otherwise of the cushion, it is my belief that no track should be built with underbanking in excess of 10' less than that called for by a design speed of 52.67 kph (=1:50.0 mile rate).
Anecdotal evidence suggests that there are major differences in speed and injury-proneness among different tracks. As a general rule, the faster the track record, the safer the track. The reason for that association is that poorly designed tracks prevent horses reaching their full speed potential because of pain.
One reason that there are so few "optimum" tracks is because the difficulty of track construction and the ongoing costs of track maintenance vary inversely with the size of an optimally banked track. A 1,000-meter track optimum for a mile rate of 1:55.0 would have curves of 92 meters radius and bank angles of 12 degrees.
Where the site is constrained by the topography the curve radii may, of necessity, be too small to allow optimum bank angles to be used with conventional surface technology. For a design speed of 52.67 kph (=mile rate of 1:50.0), the 74-meter radius turns would require a bank angle of 17.32 degrees. It is unlikely that such a steep bank angle could be economically maintained with conventional track construction techniques.
The single most important statistic for a track, from the safety point of view, is the "design speed" of the track. The design speed is defined as that speed at which a horse can negotiate the tightest bend on the track without leaning in relation to the track surface; in other words, the speed that will allow the horse's vertical axis to remain at 90 degrees to the lateral track surface on the tightest bend.
It is desirable that the design speed become the standard track rating system throughout the world. It is based on easily determined and fixed characteristics of tracks; it has the advantage that it is not susceptible to the hyperbole with which tracks are often described by enthusiastic operators; and it gives participants a pretty good handle on what is really happening.
The other useful aspect of the design speed is that it is that unique speed at which there is no tendency for a sulky, mobile barrier, or any other wheeled vehicle to slide across the track. Thus the driver of the mobile will know that maintaining that speed through the turns in slippery conditions will minimise the risk of sliding sideways. He will also know that the greater the difference between the track design speed and his actual velocity through the turn, the greater will be the tendency for his vehicle to slide across the track.
As for the mobile, so for the sulky. In wet and slippery conditions, such knowledge may become a vital safety consideration. In order that participants know the track design speed, it should be displayed prominently in terms both of mile rate in minutes and seconds and of velocity in kilometers per hour.
At all velocities other than the track design speed, the tendency of a vehicle to slide laterally will be resisted by the friction between the fires and the track surface. The combination of wet weather and track surfaces with high clay content may dramatically reduce that friction by comparison to that applying to a hard (especially unconditioned) surface under dry conditions.
Equally, at velocities above the design speed, the sulky will tend to slide up the bank and away from the inside of the track, while at velocities below the design speed the sulky will tend to slide down the bank and toward the inside rail. And as Kelsall (1980) noted, "Some ingenious scientific studies were carried out at the Royal Veterinary College in Sweden, to measure the strain to the fetlock joint which is caused when trotters travel at different speeds around curves with various amounts of super elevation. The results were first published in 1973. As would have been expected, the studies showed that the strain was progressively decreased as the super elevation on the track was increased, and it was eliminated when the amount of super elevation was sufficient to fully counteract the centrifugal force (i.e., when the actual speed matched the track design speed)."
From the point of view of safety, the above demonstrates again the very considerable value of knowledge of the track design speed to trainers and drivers. The trainer will know that at the design speed and no other, the strain on his horse's fetlock joint will be eliminated. If the track has properly transitioned turns, then keeping the horse to the design speed will also eliminate those "locomotory disturbances predisposing to lameness." Surely there must be few more essential pieces of information for a horse trainer to know?
It should be appreciated that the greater the demand made on the tires to provide the centripetal force in the turns, the greater will be the drag or rolling resistance experienced by the wheels and the greater must be the horse's energetic cost of locomotion in overcoming that drag. In simple terms, the greater the difference between the horse's actual speed and the design speed of the curve, the greater the force exerted against the sulky tending to resist the horse's efforts to pull that sulky around that curve. This also is useful knowledge for training, racing, and time trials.
With the greater use of track conditioners to prepare the track surface comes a greater drag penalty as actual speed diverges from the track design speed. Thus, the track designer is faced with the difficult-and for many, impossible-task of designing curves with radii less than 90 meters but with sufficient banking so that the design speed approximates the actual speeds of modern pacers, while at the same time incorporating a free-draining surface that will resist transport during heavy rain. Perhaps it is precisely this combination of difficulties with small tracks that has led to the continued popularity of 1,400- to 1,609-meter tracks (most notably in the U.S.) up to the present day.
A 1,400-meter track, built to Fredricson's bend-to-straight ratios, would have straights of 296.46 meters and turns of radius 129.7 meters. With a bank angle of 10.2 degrees its design speed would be 54.45 kph-quite satisfactory at current velocities.
Since it seems to be the case that the maximum bank angle that can be economically constructed and maintained with conventional technology is about 10.2 degrees (18%), we should aim to encourage tracks to be upgraded to that bank angle. Even tracks with 61-meter radius turns would be within 10' of a 52.67 kph design speed (1:50.0 mile rate) at such an angle, and thus would be relatively safe for horses.
The latter would have a design speed of 37.35 kph, compared to 19.68 kph for a 2.86 degree (5%) bank angle.
Ideally, of course, we should discourage or prevent the construction of tracks with such tight turns and adopt 70 meters as the smallest turn radius permissible. A track with 70-meter turns would have a design speed of 40.21 kph with a 10.2 degree bank angle, and be 7.1 degrees off the optimum bank angle, for a design speed of 52.67 kph.
A 1,000-meter track with 90-meter radii and 10.2' of banking would have a design speed of 45.37 kph, but only be 3.6' away from a design speed of 52.67 kph. This may suggest a quite simple aim; just standardise all tracks to a 10.2 degree bank angle. It will be below the average racing velocity for any track under 1,400 meters but is the maximum that can be economically maintained with conventional technology, and it will represent a considerable speed and safety improvement over present track practice.