Notes on Track Design

[Purist]

The "Two Straights Raceway" thread, along with some of the race recordings I've watched recently, got me thinking about some particular points of track design.

Compromised Set-Up and Slipstreaming Circuits
There has been talk off-and-on about having more circuits that are NOT so middle-of-the-road, with a little bit of everything, and requiring a moderate to high downforce load for best performance. A key component of this that has been mentioned is having more tracks that force a compromised set-up, because enough of the lap is composed of long enough straights that it is beneficial to take a significant portion of the downforce off, which then makes the corners trickier, and braking zones longer.

Of course, the likely result of this is a circuit on which slipstreaming is a primary, if not the dominant, characteristic of the racing at a track. The difficult bit is that corners often take up such a large portion of the lap time that it takes quite a bit of the lap being not just straights, but long straights, to reach the "critical mass" we're looking for in order to get that compromised set-up tobe viable, and even preferred.

Here are some circuits, and rough percentages of their laps composed of long straights (here defined, generally speaking, as a straight of 800m or more). I'll try to give a spectrum here, but also show the range of tracks that all fit within the category as well.

Slipstreaming Circuits:
Paul Ricard- 3.4km/5.8km=58.6%
Monza- 4.2km/5.8km=72.4%
Spa- 4.4km/7.0km=62.9%
Le Mans- 9.4km/13.6km=69.1%
Hockenheim (old)- 4.8km/6.8km=70.6%
Enna Pergusa- 2.8km/5.0km=56.0%
Fuji (old)- 3.0km/4.4km=68.2%
Surfers Paradise- 3.2km/4.5km=71.1%
Kyalami (old)- 2.9km/4.1km=70.7%
Daytona (24 Hour)- 3.86km/5.73km=67.4%

Average=66.7%

More General Spectrum:
Elkhart Lake- 3.5km/6.5km=53.8%
Interlagos- 2.3km/4.3km=53.5%
Catalunya- 2.0km/4.7km=42.6%
Sepang- 2.55km/5.55km=45.9%
Indy (F1)- 1.92km/4.20km=45.7%
Monaco- 1.2km/3.3km=36.4%
Melbourne- 2.8km/5.3km=52.8%
Suzuka= 3.1km/5.8km=53.4%
Long Beach (1999)- 1.68km/2.94km=57.1%
Estoril (1994-98)- 1.90km/4.36km=43.6%

Average=48.5%

At certain tracks (like Monaco), the 800m thing isn't really going to apply, and you have to be relative about it. Also, there will be the occasional straight that will count, even though by itself, it's too short, because the entry speed onto it from the preceding corner makes it work as though it were a longer straight (like a few places at Spa). And then you have "straights" or straights joined by exceedingly fast and/or flat-out corners (like the back side of Paul Ricard).

On the matter of what makes slipstreaming circuits, the critical value seems to be around 60% of the circuit being formed by "long" straights. This appears to be the tipping point for deciding to go with significantly less downforce/drag in order to maximize top-end.

And, of course, there is not a perfectly clean delineation. The Indy F1 road course is so dominated by that one flat-out section that it could be argued that that is something of a slipstreaming circuit. Interlagos could be considered a borderline slipstreaming circuit with its very long start/finish stretch, as well as the Reta Oposta immediately following. On the other hand, Spa has so many quick (not flat-out though) corners that it's character is not necessarily so dominated by the two primary flat-out runs as is the case with some of those other slipstreaming circuits.

BTW, these are not perfect calculations. There are estimations involved, but the above figures should communicate the general idea.

I will have a few more topic areas to bring up as we go along, so stay tuned.