Explanation ... of confusing hazard lines
The pictures showed where a car (in lane 2 on approach) turned left at the roundabout, hitting a car (in lane 1) which was going ahead.
I think the red car saw the single hazard line to the immediate right of the 'what3words' marker tile (at ///skins.dame.parade), and connected it to the first hazard line in the exit road on the left (which confirms there are two lanes on the roundabout and two lanes in the exit road). It hence took the red or yellow line, so crossing the green line ... and hitting the green car.
But the single hazard line in front of both cars as they approach the roundabout is to lead lane 1 from the approach road into lane 1 on the roundabout and lane 2 of the approach road into lane 2. This maximises traffic flow through the junction by keeping traffic going ahead separated into two columns as it accelerates over the Give Way line onto the roundabout.
The presence of two lanes in the exit road left is to similarly maximise flow of traffic on the roundabout, which is approaching from the right and already in two lanes, by also keeping those two columns of cars separated.
The two single overlapping hazard lines (to the right of the roadname "Swakeleys") is the likely cause of confusion by the red car. The one (starting close to the "w") is for ahead traffic from the approach. The one (which ends close to the "y") is for roundabout traffic about to leave. The curvature most parallel to the road edge at that point tells you which is which. Drivers should always look for the line that’s straightest from their point of approach. That’ll be the one intended for them. It’s the same logic as on unmarked roads: your own line should stay parallel to the edges of the road (or hazard lines) and follow its curve.
So, the red car should not have turned left following the red or yellow line. And, because there were no lane arrows on either approach lane, the green car was correct in going ahead.
The red car is further likely to have been affected by the dirt pattern (confirming typical traffic direction) around the approach/exit junction: the surface of lane 1 on the roundabout seems much less used. So, although each local authority has delegated leeway to apply the guidance for marking/signage within prescribed limits, a series of dots to guide cars into the best position on the roundabout (such as at w3w ///give.fire.random) WON'T be painted because any traffic collisions do not cost sufficient public money to merit it.
I think the red car saw the single hazard line to the immediate right of the 'what3words' marker tile (at ///skins.dame.parade), and connected it to the first hazard line in the exit road on the left (which confirms there are two lanes on the roundabout and two lanes in the exit road). It hence took the red or yellow line, so crossing the green line ... and hitting the green car.
But the single hazard line in front of both cars as they approach the roundabout is to lead lane 1 from the approach road into lane 1 on the roundabout and lane 2 of the approach road into lane 2. This maximises traffic flow through the junction by keeping traffic going ahead separated into two columns as it accelerates over the Give Way line onto the roundabout.
The presence of two lanes in the exit road left is to similarly maximise flow of traffic on the roundabout, which is approaching from the right and already in two lanes, by also keeping those two columns of cars separated.
The two single overlapping hazard lines (to the right of the roadname "Swakeleys") is the likely cause of confusion by the red car. The one (starting close to the "w") is for ahead traffic from the approach. The one (which ends close to the "y") is for roundabout traffic about to leave. The curvature most parallel to the road edge at that point tells you which is which. Drivers should always look for the line that’s straightest from their point of approach. That’ll be the one intended for them. It’s the same logic as on unmarked roads: your own line should stay parallel to the edges of the road (or hazard lines) and follow its curve.
So, the red car should not have turned left following the red or yellow line. And, because there were no lane arrows on either approach lane, the green car was correct in going ahead.
The red car is further likely to have been affected by the dirt pattern (confirming typical traffic direction) around the approach/exit junction: the surface of lane 1 on the roundabout seems much less used. So, although each local authority has delegated leeway to apply the guidance for marking/signage within prescribed limits, a series of dots to guide cars into the best position on the roundabout (such as at w3w ///give.fire.random) WON'T be painted because any traffic collisions do not cost sufficient public money to merit it.