Learn hand signals and the shoulder check: ride one-handed safely, show turns clearly and see why drivers read a straight arm best. Step by step.
The honest answer: on a bike you have no indicator, so you are the indicator. A straight arm is the signal drivers understand most reliably, and the shoulder check before it is a must. German traffic law requires that you announce a turn in good time and clearly, and that you check the following traffic before lining up and again before turning [1].
A US study with 60 drivers measured how well the hand signal works. They watched videos of cyclists and had to guess what the cyclist intended. The result: only the arm signal significantly influenced correct judgement. Position on the road and head movement did not matter [2]. Fewer than a quarter of the drivers understood the bent-arm right-turn signal used in the US [2]. Important: this is a US study with US signals, so the finding about the straight arm is a transfer to Germany.
If only the arm is seen, the arm must really be straight and out for long enough.
The problem is rarely knowledge, it is wobbling. At low speed a bicycle is unstable, and looking around amplifies the rolling motion [3]. So you build the skill from the bottom up: first one-handed riding, then the shoulder check, then both together. Realistically it clicks after a few practice sessions (experience value).
Ride straight at moderate speed and first take just one hand off the bar for two or three seconds. The other hand stays relaxed but secure on the grip, index finger on the brake. Practise both sides.
Milestone (practice): 10 seconds one-handed on a straight line, right and left.
Turn your head and shoulders back, but keep the handlebars calm. The typical mistake: where you look, the bike also drifts. Practise on a line on the ground and check whether you are still on it after looking.
Milestone (practice): 5 shoulder checks in a row after which you are still on the line.
First look back, then extend the arm sideways, then look forward again. Extend the arm fully, hand open, palm facing down. Left arm for a left turn, right arm for a right turn.
The signal must be visible long enough before you position yourself. German traffic law requires that you position yourself in good time and check the following traffic again before turning [1]. Take the arm back before you steer: for the turn you need both hands.
On group rides there are separate signals for potholes, drain covers or stopping. There is no uniform standard; groups agree on them among themselves. Clarify the signals before the start and indicate hazards with the hand pointing down and a finger point.
Milestone (practice): before a turn on a quiet road you signal in good time without the bike leaving its course.
The shoulder check is the riskiest second of the whole exercise. A study with 32 cyclists found that additional tasks such as a shoulder check increased the sideways rolling motion of the bike [3]. So never do it in a tight bend, never on wet cobblestones and not at very low speed.
If you are unsure, take speed off briefly or stop rather than signalling while wobbling. Wear a helmet and practise away from traffic first. This guide explains and motivates, it does not replace supervised training.
Learn the "mirror look": do not turn your whole upper body, only your head to the shoulder, and look under the arm that is giving the signal. That keeps your weight central and you still see the rider behind. Practise first with the hand on your hip, then with the signal.
Extend the arm of the turning direction fully out to the side, hand open. The law requires that you announce the turn in good time and clearly [1]. A US study found that drivers mainly interpret the straight arm correctly [2]; few understood bent signals.
Yes. German traffic law requires checking the following traffic before lining up and again before turning [1]. Only if endangering following traffic is ruled out does the look back before the turn itself become unnecessary.
Practise on a straight, flat line at a brisk pace, because at very low speed a bicycle is more unstable [3]. Start by taking one hand off the bar for just two seconds, build up to ten, and practise both sides. This is a practice standard, not a study finding.
There is no uniform standard; groups agree on their own signals for hazards, danger spots and stopping. Clarify them before every ride. For turning in public traffic, the duty to announce under traffic law still applies [1].
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