Welcome to the GLASS Mythbusters series!
Myth: Recreational 4x4s cause 3 foot deep ruts.
Truth : Most 4x4s use tyres that are less than 30” in diameter, so have a radius of 15” or less. Even the largest tyres in everyday use are generally no bigger than 35” diameter, so have a radius of 17.5”
After taking account of the axles, differentials, brakes etc this gives most vehicles a ground clearance of around 4” to 8” and most are towards the lower figure. Therefore this is the deepest depth of rut a normal 4x4 could be expected to cause.
Major ruts are often caused by legitimate agricultural use. Some tractors cause ruts 3' deep!
Many so called “ruts” are in fact caused by water run-off eroding existing channels in the surface. Yes these can be caused initially by vehicles (recreational or agricultural) or even cycle traffic or horse drawn vehicles. Lack of maintenance especially to drainage is often the reason they can get so bad.
Ruts can allow water to run off and cause vehicles to follow the same route, especially as many unsurfaced highways are fenced or walled. Whereas pocketing on open footpaths caused by horse or foot traffic can cause standing water that makes tracks waterlogged and encourages users to divert round, making the damage wider and wider. Anyone who has walked on the peat moors of northern England will have seen this effect.