Causes Of HPDE Crashes
In my experience, crashes in HPDE events can be grouped into one of three categories:
- Bad technique.
- Improper judgment.
- Not paying attention.
In each category there are unintentional crashes, where the driver was unaware that what they were doing was potentially dangerous, and those where the driver knew, or was told but did not listen.
I believe that, excluding reckless drivers, most - perhaps 3/4 of all crashes - are a result of the driver not unwinding steering at track out, dropping the outside rear wheel off pavement with steering angle, then impacting a wall on the inside of the turn.
Another property of HPDE crashes is that they are inevitable. Even drivers who are not reckless can have bad technique, momentary lapses of judgment or be momentarily distracted through no fault of their own. The best we can do is develop driving skills and awareness faster than we develop pace and aggression, and hope that we "run out of talent" as few times as possible through our HPDE career, and with the lightest consequences possible.
Bad technique crashes are a result of a driver not driving the car the correct way. As the purpose of HPDE events is to take drivers who do not have high performance driving skills and teach said skills to such drivers, bad technique crashes are inevitable when looking at the entire universe of HPDE drivers. As a specific driver though bad technique crashes are preventable by learning correct driving technique.
Holding Steering Angle
The biggest, and most frequent, bad technique that results in crashes is drivers of higher power cars not unwinding steering on track out. Such drivers drive constant radius arcs through turns and hold the same steering angle from turn in point to track out point. This works at low speeds compared to the car's potential - as long as the car has a grip reserve, if the driver entered a turn too fast they can turn the steering wheel a bit more and fit into the pavement. The danger comes from increased speeds where the grip reserve diminishes and eventually ceases to exist. When this happens and the car does not fit into the track at corner exit, the driver continues to hold steering angle - even adding steering to try to force the car stay on pavement - but all that happens is the car drops outside wheels off pavement, and when the outside rear wheel goes off pavement the car typically experiences instant rotation and heads for the inside wall.
The most reliable cure for not unwinding steering is to always unwind steering at corner exit. Do not unwind steering because you feel that you need to do so in a particular corner - do it because this is how you always drive. Unwinding steering does not mean completely straightening the car either; the important part is starting to move the steering wheel back to center. If you are used to beginning the centering motion in each and every corner, when you go into a corner too quickly you will also start to unwind and it will be that much easier to continue unwinding as the car approaches outside edge of the track.
The second part of the unwinding equation is always completely straightening the car when it is on the outside edge of the pavement. Notice that I said "pavement" and not "when the car is about to go off". If you train yourself to always have no steering angle when the car is fully tracked out, when you find yourself running out of track you will straighten the car anyway and you will be a lot more likely to go off track parallel to the track which will then be a non-event.
Driver runs out of pavement while holding most of the steering angle and throttle - you can hear the revs going up just as the car begins to spin. Once the car is in the spin the driver certainly does not apply full brakes, it's hard to tell from the video but the driver may not have been braking at all - which meant he was rolling backwards at full speed - until impact:
Trying To Stop
Second bad technique is trying to stop the car when this is physically impossible. For example, consider a corner taken at 70 mph. Suppose you are coming in too fast. How much pavement does a car need to decelerate from 70 mph to zero? A lot, and in all likelihood more than how much pavement is ahead of you before the track turns.
I believe racers are much more susceptible to crashes resulting from attempts to stop than HPDE drivers are, because HPDE events typically see much more space between cars on average. In a race though drivers that are looking at a spun or hit car drive right into it because they are 1) looking at the car - and their hands take them where their eyes are looking - and 2) trying to come to a stop. A much more effective strategy is to figure out which side of the spun car is the safer side to pass on, and go around.
As braking is our natural reaction to questionable situations, it takes active mental effort to not brake but consider alternatives, pick one and then execute it. When you are braking, especially in a car without ABS with the front wheels locked up, the thought that should be going through your mind is when you are going to get off the brakes so that you can steer. As you are braking you should be looking for an escape route.
Ignoring Run-Off Areas
Many corners have run-off areas constructed in such a way that a car grossly overdriving said corner will be stopped without damage. It pays to know which corners have such run-off areas, and where these areas are. If you find yourself in trouble, such as losing brakes prior to a corner, you should try to aim for the run-off area rather than blindly go off track.
Here is what happens when a driver turns away from the corner (VIR turn 1) and proceeds to miss the run-off area and its gravel trap entirely:
I happened to have a similar experience of losing my brakes coming into turn 1, but I went off straight and buried the car not even two car lengths into the sand trap that is conveniently situated just past turn 1. I thought I was going into the tire wall but I stopped well before it. A car going much faster than I was would have achieved the same feat.
To contrast, here is a video of a driver losing the brakes and going through the gravel trap. While the car did not stop in the gravel trap the gravel was responsible for most of the speed reduction:
Here is another video of a driver making use of the run-off area after losing the brakes going into turn 1 at Watkins Glen:
Sometimes there simply is not enough run-off. This is a track design problem. In the following video the driver did the best he could trying to turn the car to match the track's direction, used as much run-off as was present, and put the car in the wall squarely nose first which is generally the safest way of impacting a stationary object. Unfortunately the run-off looks like an access road rather than gravel trap and it did not slow the car down very much:
Not Applying Maximum Braking
When a car enters a spin, the safest thing to do is to apply maximum braking, ideally locking up all four tires, to bring the car to a stop without changing its direction of travel. This procedure is known as "both feet in" as in a manual transmission car it involves pressing the clutch and the brake pedals all the way down.
Most tracks have a lot of run-off room parallel to the track direction and not much room perpendicular to the track direction. Let's look at NJMP Lightning turn 1 for a great example:
The green line is the normal line through turn 1, and the cars are moving right to left. The blue line is a car understeering from prior to the apex or spinning prior to the apex and continuing in a straight line, eventually departing the track. The purple line shows what would happen should a car run out of track at the exit but maintain some steering control to be able to go into the larger run-off area. The red line shows a car whose front tires are rotating and the car follows those tires, eventually crossing the track left to right and impacting the inside wall. The blue line is easily three times as long as the red line and the purple line is twice as long as the blue line.
Here is a video demonstrating this exact situation:
Had the driver gone both feet in when the car began to spin, he likely would have avoided contact entirely.
Fixing Driving Technique
To fix bad technique, you first need to be aware that you have it. Practically speaking this means you need to have an observer in the passenger seat watching you drive. Holding steering angle is hard to spot from the outside of the car (although there are signs) but is pretty straightforward to see inside the car. As you improve your skills and increase your pace, and progress through the run groups, periodically ask experienced drivers or instructors to ride along with you to observe if you have any bad driving techniques.
This is when the driver thinks they can do something that the car cannot, or the driver does something without adequately thinking it through. Examples are:
- Shortening braking zones in excessively big steps. For example, if a driver currently brakes at 300 feet, attempting to brake at 275 feet is sensible, while at 200 feet is not.
- Driver trying to follow another car instead of driving their own line, assuming that both cars can drive the same way. Especially when the cars are very different, such as a large and heavy car trying to follow a small and light car, the following car often cannot repeat braking points and trajectry of the leading car, resulting in the following car going off track in a turn.
- Mashing thottle in a high power car without knowing how the car would react, especially while still in a turn.
The principles of good judgment are:
- Make one change in your driving at a time.
- Make changes in small increments.
- Do not assume that you, or your car, can do something someone else does.
- If in doubt, be very careful.
Bad judgment can be fixed with an instructor's help, or by the driver themselves. Having and using common sense helps a lot, as does thinking through possible outcomes before doing anything questionable. Judgment is not something instructors talk about often but instructors generally are trying to impart good judgment to their students every time instructors comment on the students' driving.
Not Paying Attention
If a driver does not look at the track, they are unlikely to stay on it. Another example is when the driver forgets which way the track turns, or how sharp some turn is.
Track driving is a precision discipline. Intermediate drivers turn in within 1-2 feet of the same point in most corners; advanced drivers turn in within inches of the same point. Looking away from the track for two seconds at the wrong time is enough to screw up car position to the point where an off is inevitable.
I am guilty of not paying attention myself, and the only remedy I have so far is trying to pay as much attention as possible, especially to the track that is coming up.
While mechanical failures are rather common at track days, impacts resulting from mechanical failures are rather rare. The impacts I have seen or experienced have been caused by:
- Wheels breaking at the spokes, resulting in a wheel flying off the car. If this happens on the front axle during turn in or mid corner the car loses most of its steering control as well as much of its braking ability and has a high chance of hitting stationary objects.
- Hubs breaking and shearing off the car. The wheel usually departs the car with the outer half of the hub causing the same consequences as a broken wheel.
- Major loss of coolant, the car can end up driving over its own coolant losing most of the grip at the affected tires.
- Aero parts tearing off the car, dramatically reducing downforce.
- Overheated brake fluid or brake pads through normal driving or seized calipers resulting in no brakes. When the brake pedal goes soft it is imperative to pump it prior to each subsequent braking zone - doing so dramatically improves the likelihood of brakes partially working as opposed to being completely gone.
- Not exactly a failure but driving over harsh curbs can move brake pads away from the rotors, and if the pedal is not pumped prior to the next braking zone the car may have virtually no brakes.
Wing falls off the car prior to VIR climbing esses:
(By the way, a 148 mph climbing esses entry is firmly in the "wow" range. A typical non-aero production car with advanced level driver will slow down to 125 mph on the entry and will continue bleeding the speed off, exiting the esses at maybe 110 mph.)
Tagged: novice, intermediate