One thought that has occurred to me is, if visibility is decent (so not thick fog) and it's daylight why could we not permit drivers to use short diversionary routes (such as the low lines that avoid Northallerton which are only a mile or so long) by driving on sight and slowly (say whatever it would take to stop up to a maximum speed of maybe 15mph). That would help keep traffic moving and would surely not be overly dangerous? Obviously something like this wouldn't work on a longer distance (for example you couldn't really drive the whole way from Darlington to Eaglescliffe to Northallerton at 15mph) but over short distances of a mile or so perhaps it could help keep trains moving?
The problem would come when some accident happens due to doing what you say, and it is attributed due to a lack of up to date route knowledge.
In the case of Northallerton, you'd still need to get onto the avoiders, which probably wouldn't have been possible in this case as you'd need to go via Eaglescliffe.