They mark the edge of the safe area, keep clear of them. In the UK red reflectors are always shown to the rear of a vehicle, never to the front, therefore they mean you are approaching the rear of car, lorry, bike etc.
on the rear
on the rear.
28-931. Lamp colors A. Front clearance lamps and those marker lamps and reflectors mounted on the front or on the side near the front of a vehicle shall display or reflect an amber color. B. Rear clearance lamps and those marker lamps and reflectors mounted on the rear or on the sides near the rear of a vehicle shall display or reflect a red color. C. All lighting devices and reflectors mounted on the rear of any vehicle shall display or reflect a red color, except that: 1. The stoplight or other signal device may be red, amber or yellow, except on a commercial vehicle, as defined in section 28-2231, the stoplight shall be red and the other signal devices shall be red or amber. 2. The light illuminating the license plate or the light emitted by a backup lamp shall be white.
You are going the wrong way on a road.
If you want to ride after dark in a legal manner you need: - a white reflector facing front - yellow/orange reflectors facing sideways - and a red reflector facing rear Depending on location, you may also be required to use lights, usually white forward and red backwards. Reflectors on a bicycle are used to provide for rider safety. People who ride bicycles near automobiles use reflectors in a similar manner to headlights on a passenger vehicle. Different jurisdictions have differing requirements for reflectors on bicycles.
get a police
Generally no, but the bicycle has to be properly equipped for it. This usually means a white light and a white reflector facing front, a red light and red reflector facing rear, and orange reflectors facing sideways.
It means you are going the wrong way
Red
On the front, a white light visible for 1,000 feet. On the rear, two red lights visible for 1,000 feet, or 1 red light visible for 1,000 feet and 2 red reflectors visible from 100 to 600 feet.
concave mirrors are used as rear view mirrors and serve dentists and used as reflectors