Final answer:
On freeways with speed limits less than 70 mph, trucks and vehicles towing trailers are usually restricted to 55 mph to ensure safety. The 'de jure' speed limit is the legal limit shown on signs, while the 'de facto' speed limit may be what is informally enforced.
Step-by-step explanation:
On freeways with speed limits less than 70 mph, trucks and vehicles towing trailers are restricted to 55 mph. This is a rule that aims to maintain safety on the highways by limiting the speed of larger and potentially more dangerous vehicles, especially those carrying heavy loads or driving in conditions less optimal for high-speed travel. It is important to differentiate between the de jure speed limit, which is the legally established limit posted on road signs, and the de facto speed limit, which might be informally enforced based on the speed at which law enforcement tends to pull drivers over for speeding.
It's also worth noting that driving behaviors, such as speeding or driving too slowly, can lead to different reactions from fellow drivers, as seen in the scenario where Peter becomes frustrated with a driver adhering to the minimum speed limit in a business district.