How does the start work in BMX racing?

• The system: "a starting gate equipped with a voice box starting system".
• The call: stage 1, "ok riders, random start". Stage 2, "Riders ready" and "Watch the gate".
• The wheel: "The front wheel must be placed against the gate, be grounded and remain stationary during the starter's call".
• Lights: the gate has coloured starting lights that every lane can see.
• Stopping it: for safety the stop button can be pressed at any time up to the end of stage 2.
• Gate positions in the motos: set by a table and shown on the start lists.
• Gate positions later: riders choose. The fastest lap time in the previous round has first choice. Where times are not used, the best finishing place does.
• Late to staging: the rider loses the pick and takes the last gate left.
• The wrong gate: refusing to move to the correct position, or starting from another one, is a disqualification.
• Timing: the clock starts when the mechanism that drops the gate is activated.
• A re-run: all riders start from the same gates as before.

The glossary has the gate start and BMX racing.

A solid gate makes a false start physically impossible: nobody can leave before it falls. The random delay stops riders from timing the drop, so the start rewards reaction and not guesswork. Gate choice matters because the inside gate has the shortest run to the first turn.