Complex sentence: Its top speed was 16 miles an hour, which was above the legal speed limit at that time of 12 miles an hour however some B-types could reach 30--35 miles an hour under the right conditions.
Split into simpler sentences: Its top speed was 16 miles an hour, which was above the legal speed limit at that time of 12 miles an hour. However the vehicle could reach 30--35 miles an hour under the right conditions.