How can I talk about speed limits in Chinese? For example, how would I say, "That road has a 50 mile-per-hour speed limit?
Firstly, for the example you provided, you may say
那条路限速50英里 then I will know it is 50 miles/hour
secondly, in China the default unit is kilometers per hour for speed limit, so if you want to say "that road has a 50 km/h speed limit" you can just say