How do I give a drafting or blocking penalty on the bike?

Drafting notification (World Triathlon rule 3.4 a): as soon as it is safe:

1. sound your whistle;
2. show a blue card;
3. call the athlete's number in English and say "Drafting penalty, you have to stop at the next penalty box".

You must make sure the athlete has received the notification, which has to be clear and unambiguous (rule 5.6 b). The penalty is served in the next bike penalty box.

Other bike time penalties: whistle, show a yellow card, call the number and say "Time penalty, you have to stop at the next penalty box". Again, make sure it was received.

Blocking (rule 5.7): an athlete riding where someone behind can't pass, because they are poorly placed on the course, gets a yellow card, served at the next bike penalty box.

Escalation (rule 5.6):

• Failing to stop at the next penalty box: disqualification.
• Second drafting offence in standard distance or shorter: disqualification.
• Third drafting offence in middle or long distance: disqualification.
• Drafting violations cannot be protested.

Dangerous riding (rule 5.1): accidental contact or cutting across, followed by moving away without causing a crash, isn't penalised. Cutting across dangerously or impeding without moving away earns a time penalty. Deliberately targeting another athlete means disqualification and possible referral to the World Triathlon Tribunal. Passing on the wrong side can be penalised as dangerous riding.