Usually cyclist dismount signs are placed where it is considered to be dangerous for cyclists to continue, such as in this case, approaching or descending a steep hill.
However they are not mandatory signs, they are advisory - so although they will indicate an area where it may be safer to dismount and to push your bicycle, you are not legally obliged to do this and you will NOT be breaking the law if you choose not to do so.
Cyclist dismount signs are not considered to be particularly effective in most areas because they create friction and annoyance with road-users who wrongly assume that the cyclist is breaking the law by disobeying the instruction. They also provide no information about the hazard, and in some cases can actually make it more dangerous for the cyclist to continue (i.e. having to walk into the road to get around roadworks).
There is no specific time or a distance limit on Cyclist Dismount signs because they are not legally enforceable, so the only guideline is that you can get back on your bike and continue to ride when it is safe to do so. This could be anywhere really, depending on your viewpoint.
Whether or not it could be used against a cyclist who was involved in a no-fault accident is a very interesting question.
As the cyclist was advised to dismount, they could claim that they were following an advisory sign which led to them being involved in the accident. With an advisory sign, whether or not the cyclist dismounting was a major contributing factor would be discretionary in each case, and other things would be taken into account, e.g. whether the cyclist was travelling in an appropriate and safe manner.
It is worth considering, however, that it is far more likely that if a cyclist is involved in an accident where they have NOT followed the advice and dismounted, then they will find it much harder to prove that they were not part of the reason the accident took place.
Disclaimer: The information in the article is for general purpose information only and should not be constituted as legal advice. This article has been produced by a third party and Jardine Motors does not take any responsibility for the completeness, accuracy, or reliability with respect to the website or the information provided. Article last updated March 2016.