Roundabout Gap Judgement with a Misleading Indicator

Convert everything to time, because a gap is a time, not a distance.

• You: 15 m at 20 km/h (5.6 m/s) = 2.7 s to reach the give-way point, then 2.5 s to clear the entry lane - so you would occupy the circulating lane from about 2.7 s to about 5.2 s.
• Pickup: 25 m at 30 km/h (8.3 m/s) = 3.0 s to reach that same piece of road.

Decision: do not enter. You would arrive at the entry point about 0.3 s before the pickup reaches it - a margin far too small to be meaningful - and you would then still be there, accelerating slowly, when the pickup arrives at 3.0 s. Entering means forcing a vehicle that already has priority to brake, which is both a collision risk and a failure of the give-way obligation.

What a safe gap looks like here: the pickup needs to be far enough back that its arrival time comfortably exceeds your 5.2 s clearance time, with a margin for the fact that your acceleration estimate is optimistic with a full car. Roughly, you want it 12–15 seconds' worth of travel away, not 3.

Re-run the reasoning with the hatchback removed: the answer does not change, because the binding constraint is the pickup, not the car with the indicator on. Identify the constraint before deciding, not after.

Almost none, on its own. An indicator is a statement of intent, not a statement of fact, and it is the least reliable evidence available to you because it can be left on by accident, put on too early, or left on after an exit is missed.

Rank the evidence:

1. Position and geometry - road wheels, body angle, whether the car is drifting towards the outer edge. Wheels tell you what is happening now; the indicator tells you what the driver thought about a second ago.
2. Speed - a car slowing towards the exit is consistent with the signal; one holding 30 km/h around the circle is not.
3. The driver's head - a mirror check towards the exit is weak but supportive evidence.
4. The indicator - confirms the other three or is disregarded.

What this means in practice: in this case the indicator and the geometry disagree, which means the driver's intentions are unresolved. You wait. Pulling out in front of a car that is signalling to exit but continues around is one of the most common roundabout collisions, and the fault will be yours because that driver was already circulating.

Would anything change it? If the car were already past your entry point and clearly decelerating towards the exit, the signal plus speed plus position would agree and you could rely on it - but you would still watch the wheels until the car is actually turning out.

Sequence through the roundabout:

• Enter into the correct lane for the second exit and hold it; do not drift across lanes inside the circle.
• Maintain a speed that lets you look, not one that commits you.
• Signal right once you are past the exit before yours - an exit signal given too early misleads the driver waiting at that earlier entry, exactly the error you refused to trust in the previous task.
• Check the left mirror and blind spot before leaving the circle, because a cyclist or another car may be alongside on your outside.

At the exit: the pedestrian is 30 m past your exit and walking towards the crossing. Two things follow:

1. Plan to stop, not to accelerate away. A driver who exits a roundabout briskly and then finds a pedestrian at the crossing has to brake hard with traffic behind.
2. Scan behind before braking for the crossing - an exiting driver behind you is often still looking left at the circulating traffic and will not expect you to stop. Brake early and progressively.

The judgement being tested: the give-way obligation at the roundabout and the duty to give way to a pedestrian at a crossing are separate obligations separated by a few seconds of road. Managing them well means anticipating the second while satisfying the first, rather than dealing with each as it arrives.