it also depends on the road network in the area concerned. Newcastle to Darlington for example a bus pulls out of Central Station almost directly on to the redheugh bridge along the A184 and boot straight down the A1 to junction 58 and along the A68 to Darlington, whereas Newcastle to Darlington all stops has to come off the A1 at jn 63, through Chester Le Street town centre, up the hill to take the left turn into the housing estate to reach the station pick up point, (or along the road behind the town centre iver all the speed bumps to the hospital and in passed screwfix) then back through the town centre and on to the A167 towards Durham which involves several roundabouts, negotiate the traffic heading to an out of town shopping centre, passed the college and hospital, then up the hill to Durham station, negotiate the tight turning circle that is usually blocked by people doing pick ups and drop offs, then back down the hill, negotiate the bery narrow laned and busy Milburngate bridge to pick up the A690 and on to the A1 at jn 62 - or alternatively stay on the A167 all the way
The train takes 30-35 minutes to cover the journey and all stops, the bus can take 45 minutes non stop with no traffic, adding the stations increases it to at least one hour 10 minutes. When traffic along the A1 western bypass and A167 Darlington North Road is factored in can easily add 30 minutes to the journey, and this is an example using major trunk routes and dual carriageways. RRBs between Newcastle and Edinburgh stations have a single carriageway A1, lorries limited to a maximum 56mph and no possibiliy of passing them to contend with (I believe its 40 on single carriageway roads) I would imaging a RRB covering part of the S&C will have some very convoluted routes through and around the hills to reach each affected rail station