What significant change was observed while the national maximum speed law was set to 55 mph?

The significant change observed while the national maximum speed law was set to 55 mph was a reduction in traffic fatalities. The introduction of this speed limit was intended to enhance road safety and reduce the number of accidents. Studies conducted during the period the 55 mph limit was in effect demonstrated a notable decrease in the number of fatal crashes. This reduction can be attributed to a variety of factors, including lower speeds leading to reduced impact forces in accidents, greater reaction times for drivers, and the potential to avoid accidents altogether at lower speeds.

The effectiveness of the law in lowering fatalities is often cited as evidence that speed limits play a crucial role in traffic safety. In contrast, other options concerning traffic fatalities increasing, vehicle registrations decreasing, or fuel consumption rising do not align with the documented outcomes during that time frame when the 55 mph speed limit was enforced.