What distance from the preceding vehicle should you maintain standing before an interection, waiting for the green signal?

Why?

When stationary behind another vehicle before a junction, you must leave a safe gap suited to the situation. The photo shows vehicles waiting at a red light, so enough space should be left to avoid contact with the car ahead. There is no general minimum of 0.5 metres or mandatory range of 1 to 3 metres for this situation, as suggested by the other answers.