LIFE LINE OF THE ARIZONA HIGHWAYS

Life Line of the Arizona

THE operator of a motor vehicle must necessarily share the highways with any number of other motorists who may be using them. When any space must be shared, it is necessary to have a complete understanding as to what is a division of that space. With the above rules in mind, it becomes necessary to make regulations definitely stating just what part of the highway each motorist shall be entitled to occupy and at what times and under what circumstances he shall be allowed to occupy it. For example, an operator shall have first claim to the right hand side of the highway, but shall be permitted to use the left hand side for passing, at times when that side is not occupied by the operator to whom it belongs and when the use of it will not endanger other users. With the increased number of drivers on the highways, and with the multitudinous other things that they must constantly keep in mind, it became necessary to mark definitely the highway in some manner to indicate just what part each was entitled to, and at what times it was safe for him to "borrow" a part of what rightfully belonged to some other motorist traveling in an opposite direction. The need for such a line of demarcation has been successfully filled by the highway center line stripe and the lane markings on our multiple lane highways and streets. Designating the center line of the highway was a very simple procedure once the need of it was realized and the decision to so mark it was made; but the problem of also placing the center line stripe in such a manner that it would, in addition to showing the driver the center line of the highway at all times, show him just where it was permissible to cross over this center line when passing another vehicle traveling in the same direction, was not quite so simple.

The system of striping which employs the use of a double stripe where passing is prohibited, and the single stripe to denote stretches where it is permissible to pass, is very satisfactory. The use of stripes of a contrasting color to denote the different conditions, also had its merit. However, after weighing carefully the results obtained and the costs of these two systems, it was decided that the system of striping now used in Arizona State Highway Department, would not only meet all requirements, but that the cost of applying and maintaining such a system would be much less. The system now in use consists of a single broken stripe on the center line of the highway for safe passing and a single solid stripe to indicate at just what points passing is prohibited. The solid stripe is employed when the following conditions are encountered curves and hillcrests, where visibility is limited, approaches to railroad crossings and where the flow of traffic is extremely heavy. It is an easy matter to designate the points at which the solid stripe shall be used, such as railroad crossings approaches and heavily traveled areas, but the use of the solid stripe to denote limited visibility at hillcrests and curves is employed only after a careful study has been made of all existing conditions which would tend to make passing hazardous at these points. Much more clear distance ahead is required for passing than is generally realized. To illustrate this point, let us presume that you are following a vehicle and traveling at the same speed. In order to pass that vehicle, approximately seven seconds are required. If your passing speed is fifty miles per hour, and you pass another car traveling at forty miles per hour, you travel 7x73

Striping Machine Develed and Constructed By State Highway Department Highways

feet, or 511 feet from the time you begin to pass until you safely cut back into your own lane. While you are doing this, the vehicle you are passing travels 7x59 feet, or 413 feet. If a car is approaching from the opposite direction at forty miles per hour, when you start to pass, the space used by your car and the approaching car will be 511 feet plus 413 feet, or 924 feet. Add 100 feet as a margin of safety and you have 1,024 feet, the clear, unobstructed distance required for safe passing under the stated speed conditions. It is readily appreciated that the operator of a motor vehicle has no time to make these calculations while driving on the highway, even though the speeds of the other vehicles were obtainable, and for this reason the hillcrests and curves have been marked with solid stripes to enable the careful operators of motor vehicles to determine at what points the passing of another vehicle should be attempted.

In 1924, the Arizona State Highway Department began its first striping of highways. The equipment used at that The time consisted of a paint machine towed by a large truck and required a crew of six to eight men to operate it. The alignment of the stripe was maintained by a pilot wheel traveling along the edge of the pavement. The resulting stripe was very uneven and irregular and due to the use of paint rather than the then undeveloped traffic lacquer, had very poor wearing qualities. The use of this device was soon discontinued due to the unsatisfactory type of stripe laid and to the prohibitive cost of operation.

In August 1934, striping operations were again resumed, this time with much better results. A push type brush machine was purchased and for some time was tried out on different types of pavement, a variety of materials being used, until a traffic lacquer was developed which satisfactorily met the requirements.

In the following two years, several additional machines were purchased and by the latter part of 1936, the entire State system of paving, nearly seventeen hundred miles, had been striped. By this time it was readily seen that improvements could be made in the machines that would materially reduce operating costs and work was started on the machine now in use, illustrations of which are shown in this issue. This striping machine was developed and constructed by the Arizona State Highway Department, in the Phoenix shops, and has more than fulfilled all hopes that were held for its economical and efficient operation. The machine, including alignment indicator, (Continued on Page 17)