Are you one of those people who hate feeling locked into driving at a crawl, even when there’s nothing but smooth open roads in front of you? At least one Arizona legislator is apparently feeling the same way. On December 15, 2025, Rep. Nick Kupper introduced a bill dubbed the Reasonable and Prudent Interstate Driving Act, or RAPID Act. The bill would eliminate daytime speed limits on certain Arizona highways, with a stretch of Interstate 8 from Casa Grande to Yuma serving as a one-year pilot program before a larger rollout.
As I write this, the bill has not been voted on by the Arizona House of Representatives or the State Senate. But it’s sparking plenty of discussion everywhere from Car and Driver to Newsweek. To me, the RAPID Act raises the larger existential driving question of whether American roads still need speed limits, at least during certain situations. By looking at the specifics of the RAPID Act, the history of speed limits, and the data on their effectiveness, I’ll try to get to the bottom of this debate.
What to Know About the Arizona Proposal
The most important thing to know is that the RAPID Act (known officially as Arizona House Bill 2059) isn’t a blanket repeal of state speed limits. For starters, the intent is for the bill to apply to rural, less-traveled interstate highways, specifically stretches with fewer than 50,000 residents. Although the exact roads beyond the test stretch of Interstate 8 haven’t been determined, several other factors beyond population would be considered, including road design and historical safety records.
Second, the lack of a speed limit would only apply during daylight hours. At night, the speed limit would be 80 mph, which is still five mph above the fastest current Arizona speed limit. Furthermore, commercial vehicles such as trucks and buses would be limited to 80 mph day and night. Finally, there would be annual safety audits of each road segment, and Arizona would increase penalties for drivers who are overly aggressive, follow cars too closely, or otherwise “misuse” the policy.
Nevertheless, the proposal represents the latest step in an ongoing shift for Arizona. In the past few years, the Department of Transportation (DOT) increased the speed limits on parts of Interstate 17 and State Route 24. If the RAPID Act is passed, it would make Arizona the first U.S. state to have roadways with no speed limits since Montana abolished its short-lived “reasonable and prudent” interstate driving policy in 1999.
Why Do We Have Speed Limits?
If it feels like speed limits have been around forever, it’s because they basically have. On American shores, they date to 1652 when New Amsterdam (now New York City) declared that wagons, carts, and sleighs could not commute “at a gallop.” Connecticut enacted the first motor vehicle speed limit on May 21, 1901, setting maximum speeds of 12 mph on city roads and 15 mph on rural roads.
These limits remained up to individual states for decades, with some states moving faster than others. The biggest push came not because of safety concerns, but because of gas prices. In January 1974, in response to the ongoing energy crisis, the national speed limit was set to 55 mph. The limit was raised to 65 mph for rural interstates in 1987, and full state control of speed limits was restored in 1995. At this point, 35 states have speed limits of 70 mph or higher, with the fastest being the 85 mph “Pickle Parkway” which goes from Austin to San Antonio, Texas.
The debate over speed limits has raged seemingly just as long. There are two main arguments in favor of speed limits. Faster speeds give drivers less reaction time to avoid collisions, increase stopping distances, exponentially raise the force of impacts, and endanger other drivers on the road. Also, travelling steadily at a lower speed consumes less fuel than travelling at a higher speed, reducing operating costs and carbon emissions. This was the main incentive behind the 55 mph national speed limit.
However, there are several arguments against having speed limits, or at least raising the existing limits. Most roads are built to safely handle much higher speeds than currently allowed, which means lower speed limits unnecessarily increase travel time and traffic congestion. When left to their devices, drivers subconsciously choose a safe speed based on the situation. Known as the Solomon Curve, this improves traffic flow and reduces speed variance, which some studies have found to affect accident rates more than sheer speed. Law enforcement efforts can focus on more dangerous actions, such as using handheld devices, not wearing seat belts, and driving under the influence. Finally, with ongoing improvements in vehicle safety and fuel efficiency, these issues are less of a concern than in the past.
Are Speed Limits Effective?
For something so ingrained in culture, research on the effectiveness of speed limits is surprisingly mixed. Some studies, such as this February 2024 paper in Accident Analysis & Prevention, show a clear link between lower speed limits and reductions in crashes and injuries. In protesting the RAPID Act, the Insurance Institute for Highway Safety cited a 25-year study showing that a five-mph increase in speed limits boosts traffic fatalities by 8%. It also claims 29% of all crash deaths nationwide are speed-related, and that raising the speed limit in certain zones can cause a “spillover effect” to surrounding stretches of road.
Other studies, though, are less conclusive in favor of speed limits. A recent Minnesota DOT study found that when a posted speed limit in the City of St. Louis Park was lowered, overall traffic speed barely changed. However, speed variance increased significantly, with some people obeying the lower limit while others drove just as quickly as before. This variability is shown to be a leading cause of accidents. When introducing the RAPID Act, Rep. Kupper also cited data from the Montana Department of Transportation showing that speed variance decreased as speed limits increased.
Furthermore, other research has found that while setting speed limits is a significant piece of traffic safety, it’s not the entire puzzle. Specifically, they are most effective when combined with other measures, such as consistent limits based on road design and harsh penalties for violations. To this end, Florida enacted legislation on July 1, 2025, that could mean jail time for any driver who engages in “dangerous excessive speeding,” defined as exceeding the posted speed limit by more than 50 mph, or driving over 100 mph on the interstate.
What Is the Limit on Speed?
I see both sides of this issue. Beyond the hard data, I’ve experienced being stuck behind someone dutifully obeying a 35-mph speed limit when the roads are safe for at least 50 mph, and having to take evasive action on the highway because there’s that one person going 20 mph slower than everyone else. Then again, I’ve also seen the devastation caused by high-speed crashes or going too fast on rainy and snowy roads.
Overall, I don’t think speed limits should necessarily be abolished. That said, many limits are set by state statutes without regard for the specific roadway type, traffic conditions, or safety data. As a result, the limits often feel arbitrary, which is the source of much frustration.
As such, I would like to see states revise speed limits to numbers that make more sense. Perhaps they could also introduce variable speed limits, lowering them only when necessary for safety, such as during rush hour, at night, and during rainstorms. Either way, I’ll be interested in seeing whether the RAPID Act is enacted and, if so, whether the pilot program yields satisfactory results for Arizona to proceed.
