In almost all situations, it is easiest to apply the British road standard (keep left: A), overtaking to the right of the slower user. However the following reasons change this in situations other than two cyclists passing in opposite directions:
- Paths that are narrow, uneven, under bridges, or overgrown cause cyclists and other users to move to centre or vary their position.
- Pedestrians following the roadway rule of walking facing oncoming traffic (e.g. on their right)
- Pedestrians following the 'pavement' total lack of rules. (though I always keep left there too...)
- Cyclists following the old 'pass pedestrians on the water side' rule (intended to avoid handlebar snagging)
The assumption of other's knowledge of standard roadway rules is also affected by:
- Increased liklihood of use by young/ old / inexperienced/ non-road users.
- Decreased spacial awareness by leisure use joggers, cyclists etc. using music/headphones; Age- or high-volume related hearing deterioration.
Therefore, it is easy and always best practice to slow down and signal (or call out 'passing on your left/right') to avoid collisions, crashes and dirty looks. This also works even on the rare cyclepaths with lane and direction markings.
Remember, just as cyclists come off worst in a road collision because everything else is bigger, everything else on a cyclepath (pedestrians, buggies, prams, fishermen, jakeys, cats) come off worse as they are smaller. Don't become the arse you're trying to avoid on the roadway.