Extracted from the 2015 FIA World Rally Championship Sporting Regulations

40. COMPETITOR SAFETY
40.1 EQUIPMENT OF THE CREWS
Whenever a car is in motion on a special stage, the crew must wear homologated crash helmets, all required safety clothing and equipment in compliance with Appendix L Chapter III - Drivers’ Equipment as intended by the equipment manufacturer and have their safety belts fastened. Any infringement will be penalised by the clerk of the course who may also refer the matter to the Stewards.

40.2 SOS/OK SIGNS
40.2.1 Each competing car shall carry a red “SOS” sign and on the reverse a green “OK” sign measuring at least 42 cm x 29.7 cm (A3).
40.2.2 In the case of an accident where urgent medical attention is required, when possible the red “SOS” sign should be immediately displayed to the following cars and to any helicopter attempting to assist.
40.2.3 Any crew which has the red “SOS” sign displayed to them, or which sees a car which has suffered a major accident where both crew members are seen inside the car but are not displaying the red “SOS” sign, shall immediately and without exception stop to render assistance. All following cars shall also stop. The second car at the scene shall proceed to inform the next radio point. Subsequent cars shall leave a clear route for emergency vehicles.
40.2.4 In the case of an accident where immediate medical intervention is not required, the “OK” sign must be clearly shown by a crew member to the following vehicles and to any helicopter attempting to assist.
40.2.5 If the crew leaves the vehicle, the “OK” sign must be displayed so that it is clearly visible to other competitors.
40.2.6 Any crew which is able but fails to comply with the above rules will be reported to the clerk of the course.
40.2.7 The road book shall contain a page giving the accident procedure.
40.2.8 Any crew retiring from a rally must report such final retirement to the organisers as soon as possible, save in a case of force majeure. Any crew failing to comply will be subject to a penalty at the Stewards’ discretion.
40.3 ACCIDENT REPORTING
If a crew is involved in an accident in which a member of the public sustains physical injury, the procedure as laid down in Art. 40.2.3 must be followed.
40.4 RED TRIANGLE
40.4.1 Each competing car must carry a red reflective triangle which, in the event of the car stopping in a special stage, must be placed in a conspicuous position by a member of the crew at least 50 metres before the car’s position, in order to warn following drivers. Any crew failing to comply may be subject to a penalty at the discretion of the Stewards.
40.4.2 This triangle must be placed even if the stopped car is off the road.
40.5 YELLOW FLAGS
40.5.1 Electronic yellow flags
a) Yellow flag lights will be used in all competing cars. When the electronic Yellow Flag is activated from rally control, the Yellow Flag LED light situated on the FIA Emergency Console will flash and a continuous alarm will ring in the cockpit. Crews must confirm acknowledgement of the electronic Yellow Flag by pressing the OK button as soon as they see it and must immediately reduce speed.
b) The FIA-approved Yellow Flag LED system to be used will be provided by SIT only.
c) The Yellow Flag LED must be visible by both crew members.
40.5.2 Yellow flags at radio points
The yellow flag will be displayed to crews only on the instruction of the clerk of the course. The flags may only be displayed at radio points marked in the road book and by a marshal wearing a distinctive jacket of the colour stipulated in Appendix H and on which is marked the radio point symbol. Flags will be displayed
40.5.3 Meanings of a yellow flag
On passing a displayed yellow flag and/or acknowledging an electronic yellow flag, whichever happens first, the driver must immediately reduce speed, maintain this reduced speed until the end of the special stage, and follow the instructions of any marshals or intervention car drivers. Failure to comply with this rule will entail a penalty at the discretion of the Stewards.
40.5.4 A crew which has been shown the yellow flag will be given a notional time for the stage, as in Art. 39.
40.5.5 If different signalling systems (e.g. flashing lights) are used in super special stages, full details must be included in the supplementary regulations.
40.5.6 If a stage is interrupted or stopped and the crews are required to pass through the special stage, a yellow flag must be displayed at the start to inform the drivers how they must proceed.
40.5.7 Yellow flag points during reconnaissance
During reconnaissance, a sign bearing the radio post symbol must be displayed at the location of each radio point. This sign may be smaller than that used in the rally but must be clearly visible to crews performing reconnaissance in order that the locations may be noted.