Ride according to the road width, road layout, traffic conditions, weather, your speed, etc.
THERE ARE NO HARD AND FAST RULES WHICH FIT EVERY CONDITION.
Fix spikes to your axles so you can take them out properly.
Don't be surprised when three motorists try to kill either you or themselves in the course of a one-hour ride.
Today I had...
1. Car overtaking me uphill on narrow road, causing oncoming vehicle to brake hard to avoid collision.
2. Another car overtaking around 10 metres before blind 90 degree bend, putting him in oncoming lane as he went round corner.
3. Driver so intent on turning right at lights before they went red that she almost wiped me out.
... just wanted to vent.
urban roads are safer
possibly true as in the lower speed of most traffic on the majority of urban roads means that accidents tend to be of the cuts, bruises and breaks that will heal type whilst collisions at high speed on rural country roads and main roads figure in the KSI (killed or seriously injured) data
what p155es me off about some urban cycle routes is that to avoid the type of urban road that is potentially life threatening to cyclists signed routes will skirt through industrial estates, roads packed with parked cars and building entrances, junctions with poor visibility etc etc - resulting in potential (or actually in ) more minor accidents - rather than try to improve the ability of those in metal boxes to share space on the straight line routes