Dynamic envelope

'Dynamic envelope' refers to the typical space someone takes up while cycling. It will be larger than the static width because people will 'wobble' while travelling along. 

The DfT's LTN 2/08, Cycling Infrastructure Design, suggests that above 7mph the 'dynamic envelope' of someone cycling will be 0.2m wider than their static width. Below 7mph, it will be even larger - at 3mph, deviation from a straight line may be as much as 0.8m.