Q595: How can I tell what the speed limit is?
Maximum speed limits are displayed by circular signs with red borders. The signs may be displayed on poles at both sides of the road or on lampposts /polls along the road. On motorways the speed limit may be displayed on signs above the carriageway.
The presence of street lights generally means that there is a 30mph (48km/h) speed limit unless signs say otherwise.
The link below lists the speed limits applicable to different vehicles: