Lateral Separation

Recently, in the Radical at Laguna Seca, I had an interesting experience which highlighted one of the hazards of racing online.

I qualified on the second row, and in the early laps the drivers ahead of me all got involved in incidents and I found myself in the lead. I led for much of the race, driving carefully, staying within my limits, but near the end I could see another car closing on me.

Knowing how difficult it is to pass on this track, I decided it was better to keep running at a safe pace and let the other car catch me than try to speed up and risk throwing it off the track.

But when he caught me he followed very close behind me and when I braked, the other car hit me. This happened twice, first entering the carousel and then again entering the hairpin. The second hit pushed me so far off line that the other driver was able to just drive right by. The collision also bent my rear suspension, and after that I was off the pace. Luckily I still managed to finish second.

In a discussion afterward it became clear that the other driver was unaware of at least one of the collisions. From his perspective there was no contact.

This incident shows how much of an effect a little latency can have on the respective experiences of two drivers racing together in iRacing.

Let's imagine that you and I are racing. Even if both of us have good connections it takes a fraction of a second for the position and velocity information to make it from, say, my computer to yours. The iRacing software has to predict where it thinks my car is going to be and display that to you; by the time it gets the real information from your computer through the server, you've already moved some distance.

The result is that sometimes there are small discrepencies between what iRacing makes a remote car do (based on the iRacing software's prediction algorithms) and what the remote car actually did.

In this case, I braked but iRacing on the other driver's computer didn't predict precisely when I did that. It apparently didn't show me braking until a faction of a second later. He presumably braked in time to avoid my predicted car, but not in time to avoid my real car.

At my end, the prediction code on my machine failed to predict the precise moment when he braked. His car didn't slow on my system until a fraction of a second too late. Instead, his "predicted" car thumped into mine, pushed me off line and bent it.

I think the lesson to take from this is don't follow closely directly behind another car, especially when approaching a braking zone. Either leave a larger gap, or - and this is what I try to remember to do - establish what fighter pilots who fly tight formation call "lateral separation." As you are moving down the straight toward the braking zone, ease over to one side of the car you're chasing. Usually this will be the inside. This way, if the car ahead brakes earlier than you expect, you'll just shoot by on the inside. If it doesn't, no harm done.

You can see pro drivers do this all the time on TV. The announcers get excited and yell "he's taking a look down the inside!!" Maybe, but that's only part of the story. The driver is actually establishing lateral separation to avoid the possibility of rear-ending the other car if it brakes earlier than expected.

This is especially important if you are not familiar with the driving habits of the driver ahead. Some drivers are dead consistent, braking at precisely the same point every lap. But this is rare. Most drivers vary their braking points by a few feet either way. Later one lap, earlier the next. You can't safely follow most drivers very closely; sooner or later you'll hit them.

Moving to the inside on the straight before the braking zone has a secondary benefit: it serves as a signal to the driver ahead that you'd like to pass. In many situations, such as lapping a slower car, this is of real value. You're asking politely for a pass, which tends to make the driver ahead more inclined to give you the corner.

When you're dicing for position late in a race, as that other driver and I were, the leading driver is likely to be less willing to let you by, but on the other hand this move can ramp up the pressure a bit and make it a little more likely that the other driver will make a small mistake which will give you the position.

When following a slower car, the lateral separation tactic is the best option, IMHO. There's little or no downside, and the upside is a safer and more fun race for everyone.