Success is all about being in the right place at the right time ….. and the axiom is a guiding principle for designers of motor sport circuits. To avoid problems you need know where and when things are likely to go wrong before cars turn a wheel –and anticipating accidents is a science.
Take barriers, for example, there is little point erecting them in the wrong place –but predicting the right place is a black art. The FIA has developed bespoke software, the Circuit and Safety Analysis System (CSAS), to predict problem areas on F1 circuits.
Where and when cars leave circuits is due to the complex interaction between their design, the driver’s reaction and the specific configuration of the track, and the CSAS allows the input of many variables-lap speeds, engine power curves, car weight changes, aerodynamic characteristics etc –to predict how cars may leave the circuit at particular places. The variables are complex. The impact point of a car continuing in a straight line at a corner is easy to predict, but if the driver has any remaining control and alters the car’s trajectory, or if a mechanical fault introduces fresh variables, its final destination is tricky to model.
Modern Tyre barriers are built of road tires with plastic tubes sandwiched between them. The side facing the track is covered with conveyor belting to prevent wheels becoming snagged and distorting the barrier. The whole provides a deformable ‘cushion’ a principle that has found its way to civilian roads. Barriers made of air filled cells, currently under investigation may be the final answer. Another important safety factor is the road surface. Racing circuits are at the cutting edge of surface technology, experimenting with new materials for optimum performance.
The tracks used in motor sport all are designed to meet certain standards. If a new circuit will ever be used for an international event, its design and layout must be approved by the FIA, before any construction commences. For a permanent circuit, a member of the FIA must inspect it no more than 90 days before a World Championship event, giving adequate time to implement changes.
All design criteria, for curves and straight sections, do not mean the actual track itself, but the actual trajectory followed by the cars whilst racing. Track width on a permanent circuit should be at least 12 meters and should not exceed 15 meters This avoids bad congestion in corners by limiting the width of the approach to the corner, and having a wide enough track through the corners. There should be 3m minimum clear space along both sides of the track, usually consisting of grass. The maximum length of any new permanent circuit should not exceed 7km to allow drivers to be able to familiarize themselves with all corners on the track. The minimum length of a Formula One circuit will not be less then 3.5km, with the race being no longer than 2h 45min. Cross fall across the track for drainage purposes should not exceed 3%, or be less than 1.5%, either from edge to edge or from the center line to each edge.
The geometry of the track should be designed using the formula set out by the FIA in Appendix O to the International Sporting Code section 7. These formula give design criteria for longitudinal profile, visibility, curves, track edges, runoff areas and starting grid specifications. Curves must not get tighter as the turn progresses unless the speed through the corner is less than 125kph, and should preferably have an increasing radius. The maximum number of cars allowed to start in an international race takes all the above geometrical constraints into account, along with the types of cars competing. The number of cars allowed to practice is 20% greater than the number actually allowed to start.
The criterion for barrier placement is stated in section 8 of the above code. If "the probable angle of impact is less than 30o then a continuous, smooth, vertical barrier is preferable, and where the probable angle is high, a system of deceleration (eg. gravel bed) and stopping (eg. tyre barrier) devices should be used." (FIA Appendix O, in appendix 2)