Q595: How do I know what the speed limit is?
When entering a new speed limit the limit is displayed on circular signs at the side of the road. If there is street lighting you can presume the speed limit is 30mph unless it is signposted otherwise, in which case there will be repeater signs reminding you of this. Note there is no requirement to have repeater signs in a 30mph limit. However, care must be taken because 20mph limits in built up areas are becoming increasingly common.
On roads where the national speed limit sign is displayed, the actual speed limit you must comply with will vary according to whether the road is a single or dual carriageway and if your are driving a car or a light or heavy goods vehicle. See website in related information for the speed limit table.