Dubious Traffic Engineering and Politics Predominate Over Public Safety on Arizona Roadways

People place blind trust that the governments responsible for determining speed limits are qualified and have conducted a proper analysis to arrive at the correct number. Many firmly believe that driving even just a little above the posted limit can be indeed be extremely dangerous. But this new video on Youtube shows that posted speed limits we see are sometimes nothing more than the result of a political whim, as in the city of Peoria, AZ the limits are established by ordinances that are established by the city council. Although difficult to see, the video shows a roadway in North Peoria, the stretch of Pinnacle Peak between 83rd Ave & 91st Ave where speed limits are set for 30mph going Westbound, but 45 going eastbound. There is no discernible difference in each side of the road (low density residential with no schools or school crossing), and the road is one lane in each direction. What could the engineering justification possibly be to call for a 15mph difference in speed limits based only on what direction you’re going? The only reasonable answer is that the city wants to create a speed trap.

The video also shows another location just south of Happy Valley Road on 91st Ave. As you approach the 3-way intersection, the last 1/8 of a mile drops from 40mph to 30mph. When you turn from Happy Valley onto 91st Ave southbound, you can go 45mph for the 1st 1/8th mile, then the limit drops to 30mph for about 3/8 of a mile, then raises up to a standard 40mph limit. Again, there are no schools and no discernible changes in road design or neighborhoods over these distances. These limits are nothing more than a speed trap, and nothing more than city officials screwing with drivers.

What’s interesting is how all of this sharply contrasts with information published by ADOT about speed limits.

Since most citizens can be relied upon to behave in a reasonable manner as they go about their daily activities, many of our laws reflect observations of the way reasonable people behave under most circumstances. Traffic regulations are invariably based upon observations of the behavior of groups of travelers under various conditions.

Generally speaking, traffic laws that reflect the behavior of the majority of vehicle operators are found to be successful, while laws that arbitrarily restrict the majority of drivers encourage wholesale violations, lack public support, and usually fail to bring about desirable changes in driving behavior. This is especially true of speed zoning.

ADOT continues to explain that reducing speed limits will NOT change traffic speeds and will not change accident frequency and that there is no “direct relationship between posted speed limits and accident frequency” and that, “speed in itself is not a major cause of accidents.” ADOT then proceeds to identify such locations as those described in North Peoria as a speed trap:

It is accepted within the traffic engineering profession that there is a demonstrated need to produce as much uniformity as possible in the traffic flow and to eliminate the so-called speed trap. A speed trap may be defined as a street or road which is wide enough, straight and smooth enough, and sufficiently free of visibility limiting obstructions to permit driving a certain speed, but where the law nevertheless calls for a much lower speed.

According to ADOT, “Speed zoning in Arizona is based on the widely accepted principle of setting speed limits as near as practicable to the speed at or below which 85 percent of the drivers are traveling.” But after spending a few minutes on the side of the road at either of these locations one can clearly see that the 85th percentile speed is closer to 40 or 45mph (common on Phoenix-area arterial roads) than the 30mph displayed on the speed limit signs.

So why is the city of Peoria so careless about road safety? There are only a few possible answers:

  1. Arrogant and/or incompetent city council who either believes they are qualified traffic engineers or that they know more than traffic engineers.
  2. They have allowed incompetent city traffic engineers to remain employed.
  3. They are more interested in revenue generation from speed traps than safety.

For clues to the answer, we can look to other city council decisions. Over 3 years ago, Peoria started a pilot red light camera program at 4 intersections. The results were disastrous, leading to over a 100% increase in accidents. But for some reason (read: $$$), the city decided to renew and extend the “pilot” program multiple times (guess they don’t understand what you’re supposed to do when a pilot program fails). Finally after 3 years and continued disastrous results, the city reluctantly ended the dangerous cash cow red light camera program after being unable to justify the program under the guise of safety any longer.

But the city of Peoria isn’t alone in the world of dubious traffic engineering. Take the new stretch of 303 West of I-17 for example. This is brand new freeway, 2 lanes in each direction separated by a significant distance. This stretch has very few on and off ramps, and very little traffic. Yet the speed limit is only 55mph! Contrast this to the 101 freeway which has a great deal of traffic and is usually crowded, on and off ramps every 1 mile, and the limit is 10mph faster. I don’t think you have to be an engineer to know that the new stretch of 303 freeway is every bit as safe as the 101, if not safer. So why the lower limits?

Arizona Revised Statutes, Section 28-702 allows the establishment of speed limits on the State Highway System “upon the basis of an engineering and traffic investigation.” The MUTCD also requires a traffic engineering study. So where is this engineering and traffic investigation that found a speed limit of 55mph to be appropriate on the 303 but not on the 101?

State and local governments have become lazy, arrogant, and exploitative. They have forgotten that their purpose is to serve the people and do what’s in the best interest for the public rather than the government. ADOT’s own literature contradicts their actions and appears to violate state law. This isn’t about safety. It’s about what it’s always about: power and money.

One Comment

  1. atfsux
    Posted December 20, 2011 at 6:56 am | Permalink

    The reasoning behind the limits is that before Happy Valley was connected through from 83rd Ave. to 91st. Ave, and the 303 Loop connecting through from Vistancia out to the I-17,…is that heavy, heavy rush hour traffic ended up every day cramming Pinnacle Peak and 91st Ave. All of this in a residential area. I used to take that same drive to and from work every day during those times, and got damned scary at times. I witnessed several crashes along those streets, and was nearly in one myself that occurred right beside me. They all involved cars coming out of the residential inlets onto 91st or Pinnacle Peak, and were caused by drivers mis-estimating oncoming vehicles speed and distance, or just flat didn’t see them at all. Thusly, as accident data on these streets grew, city engineers were able to determine where they happened most frequently, and lowered speed limits on those particular stretches in direct relation to the data that suggested higher risks on those sections. Had your film been made during 4pm to 5pm in 2006, what I am describing would be obvious. The traffic flow now is very different, and the old speed limits are no longer justified. But getting back freedom is never as easy as losing it.

    –admin: Not exactly true. I drive these roads every day and the traffic has never been that heavy and there is NEVER a case where, without a median, the limit going one direction is different than the limit going the other direction, and especially with a difference of 15mph which is extreme.


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