I am a 10-year veteran long distance over-the-road professional driver of 18-wheel trucks and a 4-year resident of Payson. I have driven 80,000-pound trucks in all 48 states in every weather condition imaginable, including one hurricane. I have over 1 million accident-free miles behind me.
When it comes to mountain downhill grades, extra caution and care must be exercised.
The driver must understand that the vehicle's weight is going to "push" him/her down the hill. It is a phenomenon called "gravity." Some drivers call it "Mexican overdrive" or downhill with a tailwind. This may not be politically correct, but that is the way it is.
As the steepness of the downhill slope increases, the "push" from the weight of the towed vehicle increases proportionately. This causes an increase in speed of the vehicle.
The heavier the vehicle, the faster it will accelerate. I have driven the Slate Creek Grade many, many times over the years with a fully grossed (80,000-pound) 18-wheeler and never have had a problem with it. If you are in the proper gear with the compression brake on full and going 35 mph at the top of the Slate Creek Grade, with a 80,000-pound load, it should require braking only 6 times in the entire 5-mile stretch, to prevent the vehicle from exceeding 35 mph.
In the commercial driving schools, students are taught to approach downhill grades no faster than 35mph, empty or loaded and in the proper low gear.
Every state, including Arizona, posts signs indicating the steepness of the grade in percentage and length in miles. The Slate Creek grade is no exception. It is posted seven percent, five miles. This number is not entirely correct. It actually is seven percent, two miles with a short 100 yard, three percent relatively flat area, then 6 percent for three miles. The place where the gasoline tanker hit the retaining wall was near the bottom of the seven percent, two mile portion of the 5-mile grade, at the point where the road makes curve to the right.
The posted speed limit is 55 mph with a couple of 50 mph yellow advisory signs for the curves. This is entirely too fast for any 18-wheel truck, empty or loaded. It is also too fast for any four-wheeler pulling a trailer or a six-wheeler pulling a camper.
The mandatory maximum speed for all vehicles towing trailers on a six percent or higher grade should be 35 mph.
Several states such as California, Oregon, Washington, Idaho, Utah, Wyoming, Virginia, West Virginia, Pennsylvania, New York, etc. have significantly reduced the number of downhill accidents by as much as 70 percent by installing mandatory pull-out areas at the top of the grade.
These pull-out areas have a huge map of the downhill grade erected, showing the percentage of grade, curves, and length. In addition, the speed limit is posted with a warning of what the fine will be if you exceed it.
For example, the Grapevine in California which is located on Interstate 5 and on Interstate 80 between Truckee and Sacramento, these signs are in place with the fine posted at $1,000. It works very well. Crashes on both sides of the grade have dropped 80 percent.
Wyoming has had such a problem with vehicles of every type going too fast for weather conditions that they are installing digital speed limit signs. The speed limits will vary according to the weather and will be controlled by the Highway Patrol. They are also enlisting aid from volunteers who will be trained to give road condition reports.
Aggressive safety measures are possible, if there is a willingness on the part of the state to implement them. Arizona has been seriously lacking in this area.
The solution to the Slate Creek Grade is obvious:
1. Implement a 35 mph speed limit, with a hefty fine for exceeding it. The speed limit will apply to ALL vehicles towing a trailer.
2. Erect a very large information sign warning drivers of the nature of the grade ahead and the speed limit with applicable fine.
3. Enforce the limit with a high law enforcement presence or install those wonderful "Big Brother" traffic cameras.
4. Install those roadside speed measuring devices as used in construction zones that inform the drivers what their speed is and what the limit is. When it flashes, they are going too fast and remind them that they are on "candid camera."
These are my suggestions, based on observation and practical experience.
Richard G.J. Skoglund