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article number 706
article date 03-01-2018
copyright 2018 by Author else SaltOfAmerica
Our Technology, 1922 - Part 3-B: Autos - We Develop Highways
by Various Popular Science Magazine Writers

From issues of Popular Science Monthly, 1922.

* * *

An Ideal Section of the Lincoln Highway

WHAT is the perfect road? The Lincoln Highway Association has now launched a plan to build a mile of perfect roadway that shall embody the best of modern roadmaking practice, and serve as an example to be followed by roads constructed in the future.

As yet, the specifications are tentative, but the following points have been decided upon as necessary for the perfect road in level, farming country with open fields on each side:

The right of way must be one hundred feet wide, and provide for an average traffic of fifteen thousand passenger-cars at thirty-five miles and five thousand motor-trucks at an average speed of ten miles.

The roadbed must be built of concrete ten inches thick, with reenforcing steel embedded. The steel is merely to hold the concrete slabs in place and prevent cracks from spreading.

Submerged tile drains and catch-basins will replace the open ditch which in the past has been the cause of many accidents. Earth shoulders shall be used on each side of the concrete bed.

No curve the radius of which is less than one thousand feet shall be allowed, and all curves shall be super-elevated for a speed of thirty-five miles an hour.

Advertising signs shall be prohibited along the right of way, and as far as it is practicable obstructions to the vision within five hundred feet of a crossroads shall be eliminated.

In addition to these engineering specifications, the ideal road will he carefully and adequately lighted so that motorists may travel in the open country with dimmers on their headlights.

And, finally, the ideal section will be fenced at all embankments.

A cross section of the ideal road planned for the Lincoln Highway. It represents the latest in scientific road construction.

Cylinder Tests Subgrades

INFORMATION as to the uniformity of the subgrade under different sections of a highway, and an excellent opportunity
to gather valuable data on subgrade conditions, including expansion, contraction, bearing power and moisture content, is afforded by the testing apparatus designed by the Illinois Highway Department.

The subgrade-testing cylinder consists of a 1 1/2 by 1 1/4 inch black iron reducer, a short length of 13-inch black iron pipe, a 1 1/2-inch countersunk black iron plug, a special 1/4 by 1 1/4 inch brass bearing-plug, a short sleeve of 1-inch black iron pipe and a 1/2 by 1 1/4 inch brass disk.

The brass plug is flush with the top of the pavement and the disk rests freely on the sub-grade. The length of the pipe and sleeve varies with the thickness of the pavement in which the cylinders are used.

The brass disk follows the downward movement of the pavement and the upward movement of the sub-grade, so that any
separation between the subgrade and the bottom of the pavement can be learned by measurements taken from this plug.

The difference between initial readings, taken as soon as possible after the testing cylinders are placed, and readings taken at subsequent times, shows any change in position between sub-grade and pavement.

This simple device will test subgrades, giving data on expansion, contraction, bearing power, and also the moisture content.

Most One-Ton Trucks Travel Twenty Miles an Hour

HOW large is the average motor truck and how fast does it travel?

A census by the Bureau of Public Roads on one of the most traveled highways of New England, shows that 40 per cent of the trucks were of one-ton capacity, 33 per cent between one and two and a half tons, 5 per cent between two and a half and three tons, and less than 2 per cent of more than five tons capacity.

On a level stretch of road, the usual speed of trucks was found to be twenty miles an hour. Thirty-seven per cent traveled at this rate or faster, and one ex-speedway driver, who explained that he was in a hurry, was clocked burning up the road at forty-five miles an hour.

Let’s Hear about That Gypsy Motor Trip

WERE you one of those who answered the call of the road during the summer?

Gypsy motorists have been writing to us, telling of their experiences on their camping-trips—how much their trips cost, where they went, what lessons they learned that will be profitable to others next year, and what automobile camping equipment they purchased or improvised.

It’s not too late for you to write to us, too, telling of your experiences. For the most interesting and informative letter, $35 will be paid; for the second best, $15. Letters must not be more than 500 words long, and must be received on or before January 10, 1922.

From the June, 1922 issue. Article is titled "How We Gipsied 2000 Miles on Our Motorcycle." Picture caption: "We camped the first night in a little sylvan glaid off the main road. We found the best way to select a campsite was to drive a mile or so down some side road.

How Strange Test Highway Is Being Smashed to Bits So You May Motor on Perfect Roads

- Unique Scientific Instruments Reveal Strongest Kind of Pavement.

ONE of the great national problems that comes nearest to the everyday life of each of us is the problem of good roads. Millions are wasted annually because of the destruction of poorly built highways, and because of the lack of good roads in rural regions.

Everybody has watched, at some time or other, the best of pavements gradually breaking up, and has wondered why such damage—universally felt—-could not be prevented.

If the remarkably interesting highway-testing experiments described here serve to make the highway of the future strong enough to withstand the battering of modern high-speed and heavy traffic—as the engineers in charge believe they will—every state will reap the benefit in enormous savings and in rural development.

IN order to make America’s highways the best in the world, engineers at Pittsburg, Calif., are pounding a concrete road to bits under unique scientific test conditions. Day and night 40 heavy trucks loaded with pig iron are racing around a quarter-mile track made up of 13 sections of concrete pavement differing in design, in quality of concrete, and in the location and nature of reenforcement.

Thus the equivalent of 3000 to 4000 trucks, averaging eight tons in weight, passes over the road each day, grinding around the corners, and bumping over irregularities intentionally introduced in the surface of the road.

No pavement can stand such battering. Little by little the surface of the road is being worn out, the subgrade is giving way, the pavement is cracking.

But all this is part of the plan, and in fact, if any of the 13 sections cannot be destroyed by trucks, the army will be called upon for gun-carriages and tractors to complete the work.

- Every Weakness Is Recorded.

As the road breaks down, sensitive instruments are recording the origin and development of every cause of failure. Every crack is charted, the effects of changes in temperature and moisture are noted, and the highway engineers are confident that after the test road has been destroyed, a study of these records will show just why and how concrete roads fail.

They will know, by scientific experiment, not by guesswork, just how compact a sub-grade must be, how thick the concrete roadway should be built, and what the best reenforcement is.

The United States will spend millions of dollars this year in highway improvements. The experiments in California are to insure that a minimum of this money will be wasted, and that the new roads will be built solidly enough to support the heavy trucking and high-speed traffic now found on all our state and national highways.

To make sure that the data obtained by these experiments will be complete, 13 test sections, each representing one of the types of construction at present recommended by highway engineers, are being worked upon.

These sections differ considerably in details. The thickness of the concrete varies from five to eight inches, for example. On some sections plain concrete made up with crushed stone and cinders is used, while on other sections have been laid many sorts of reenforcement, varying in character from a layer of chicken wire placed horizontally in the binder and designed to arrest cracks, to the most elaborate structural steel re enforcements.

Thanks to four unique observation tunnels built underneath the road, many tests such as have never been attempted before are being made. In these tunnels instruments attached to the under side of the pavement are recording just what happens to the bottom of the slabs and the subgrade when a truck passes above them.

In each tunnel nine steel rods, with their upper ends embedded in the concrete, extend downward and operate the recording pens of these instruments; and so trace a complete and permanent record of every movement of the highway and subgrade upon sheets of paper drawn slowly beneath the pen-points by an electric motor. An Ames dial for recording pressure and impact is also installed in connection with each rod.

Around this quarter-mile concrete track 40 speeding trucks loaded with pig iron grind day and night, 20 racing in each direction. The type of construction that lasts longest will be used for future great American highways.

Quarter-mile concrete track.

The method of recording movements of the pavement is shown in the above cross section of the track and one of the four observation tunnels. Eight steel rods embedded in the pavement extend down into the tunnel and actuate delicate recording instruments.

Method of recording pavement movements.

The boxlike opening at the right, indicated by the arrow, is the entrance to one of the tunnels where road movements are revealed.

Entrance to testing tunnel.

Here in the interior of the observation tunnel may be seen the steel rods through which every jar on the track above is transmitted to pens and accurately recorded on moving slips of paper. Note also the Ames dials for recording pressure and impact.

Steel rods in interior of observation tunnel.

Charting the progress of a crack as it grows day by day, this engineer is gathering information of vital value to roadbuilders that has never before been studied.

Engineer charts progress of crack in pavement.

Through holes in the surface, borings of the subgrade are taken to determine its precise moisture content.

Borings in surface allow determination of moisture content.

To learn the temperature of any section of pavement, the observer inserts a thermometer into small holes filled with mercury. After the readings these holes are replugged.

Thermometer measures temperature of pavement.

Bumping over a heavy plank effectively tests road strain. The impact of front and rear wheels, as the truck passes over at 12 miles an hour, is accurately recorded by instruments in a tunnel below.

Heavy plank gives impact as trucks pass.

- Trucks Bump Over a Plank

This arrangement is particularly valuable in observing impact tests, which in the past could be recorded only by instruments placed on the surface of the pavement. A plank is placed across the road directly over the tunnel, and the trucks are driven ever it at a speed of from 10 to 12 miles an hour. The effect of the impact of the front and rear wheels is recorded on the paper by the pens below, so that a chart of the bending of the concrete slabs and the reaction of the subgrade is visible to the eye.

One result of the Pittsburg tests is the discovery that such blows are much more destructive than has been supposed. A fall of two inches—such as might be caused in actual travel by a small stone in the road—bends the entire concrete road approximately two hundredths of an inch.

If such shocks are repeated often, a crack soon develops; and since a fall of half an inch, such as might be caused by a large crack, will bend the roadway nearly a hundredth of an inch, it is apparent why roads rapidly go to pieces once they have started to break, and why prompt repairs are so essential.

- History of Cracks Charted

Great pains have been taken to record the cause and development of all surface cracks. The roadway, which is 18 feet wide, has been divided by paint-lines into six-foot squares. A crack is recorded on a chart as soon as it appears, and a progress record is kept. At present little is known about cracking in concrete, or the best means of checking it, and these charts will provide what are probably the first accurate and thoroughly reliable data on the subject.

Another test consists of driving a truck over the tunnel, stopping every few feet, and noting the bending indicated by the instruments. The results have established definitely that a heavy truck, when it is standing still, places more strain on the road than when it is moving; provided, of course, that the surface is smooth and that no jolting or impacts take place.

It is possible, in the light of these results, that no attempt will be made to limit the speed of motor-trucks on hard-surfaced highways.

In interpreting these results the temperatures of the atmosphere and the concrete are both important, and a novel method has been adopted to determine the temperature of the road. Holes are drilled here and there in each test-section. One hole reaches to a point near the bottom of the concrete pavement, a second to the center, and a third just below the surface. These holes are coated with plaster of Paris to prevent leakage, and filled with mercury.

When an engineer wants to learn the temperature of any section, he inserts the bulb of a thermometer into the mercury, and in about 60 seconds he obtains an accurate reading. After the temperature has been taken, the holes are plugged with corks, and protected from the traffic by metal caps set flush with the surface.

A method somewhat similar has been adopted to determine the effect of water on the subgrade and the rate of percolation. A ditch has been dug on each side of the pavement, so that the subgrade can be flooded until the level of the water in the ditch is on a line with the bottom of the pavement.

Before this is done, however, and while the pavement is still perfectly dry, borings are taken from the subgrade through holes left in the concrete. The normal moisture content of the soil when dry is then determined by analysis, and the borings replaced and tamped down.

From time to time after the water is turned into the ditches, more sample borings are taken to determine the rate at which the water seeps from the ditch into the soil under the road. These sample borings are made continuously during the road tests.

Meanwhile, observations in the tunnels show the relation between the moisture in the subgrade to the bearing power of the road. This is the first time tests of the kind have ever been made under such ideal conditions, and they are expected to provide data on subsoils and road drainage of great value to contractors. A rain-gage near the track, of course, measures how much natural rain falls during the experiment.

- All Trucks Weigh the Same

Another feature of the work is the care with which all trucks are loaded to the same weight to give maximum value to the results of the impact tests.

Yet to have all the vehicles of the same type is not considered desirable. The track, therefore, is subjected to the wear of wheels of all sizes, and tires of every type. The trucks are weighed on a 50-ton scale before going on the track, and while standing on the scale each is brought up to required weight by adding pig iron to its load.

On many sections the concrete has been reenforced with steel rods, similar in shape of the rods used in building. The amount of reenforcement varies from 20 to 69 tons of steel a mile.

The truck has been blamed for the rapid deterioration of our state highways. Whether it has been blamed unjustly will be shown by the California tests. If trucks do break down the roads, roads must be built stronger.

By the lessons learned in destroying the test highway, engineers expect to obtain accurate knowledge as a basis for solving the vital national—it may even be called “world wide”— problem of highway construction.

All trucks are loaded to the same weight. In the foreground is an empty truck weighing in on 50-ton scales before taking on its load of pig iron. In the distance are a number of trucks properly loaded with the iron, some of which may be seen piled near the scales.

White Road Border Makes Night Driving Safe

A STRIP of white concrete thirty-six inches wide bordering each side of a California State Highway has greatly reduced the frequency of accidents in night driving.

Every one who has driven a car in California knows that the ground often drops off steeply near the edge of the road, and the consequences of running off the road in the darkness are liable to be fatal. The white border, contrasting with the center of the roadway, gives increased visibility and warns drivers in time.

Its installation was an accident. It was decided to widen a number of the highways, and concrete of a lighter color was used in this work. The border has been found such a simple and efficacious protection against accident that it will probably become a permanent feature.

White road border gives increased visibility.

Chicago’s Municipal Parking Place Solves Problems of Congestion and Thievery

MUNICIPAL parking grounds, such as Chicago has opened on its downtown lake front area, may be a solution of the problems presented by congested streets and by audacious auto bandits that trouble the driver in every large city. The parking grounds are operated by the city. The charges are nominal.

Only the driver is allowed to enter the parking spa, and as he brings in the machine the gatekeeper gives him a card bearing the number of the auto license, This card must he produced before any one is allowed to drive out with that automobile.

Chicago municipal parking gate. © U. & U.

Air Tube Tells How to Build Roadbeds

BY means of a compressed-air tube connected with a stone slab buried under a roadbed, traffic experts can find out what happens under a road as heavy trucks pass. The tube transmits the movements of the slab, through a giant-floating metal drum, to an indicator dial. The device was invented to find out how thick roadbeds should be built.

A very thick roadbed lightens the load on every square foot of the earth or road on which it rests, since the impact on the surface is distributed over a larger area than is the case with the thinner bed. On the other band, thick roadbeds cost money. The purpose of the device is to determine how thin they may safely be built.

Compressed-air tube connects with a stone slab to find out what happens under a road as heavy trucks pass.

Highway Bridges

THE increasing importance of highway traffic, due to the development of the auto, will call for unprecedented activity in building huge bridges like the Hudson River structure with a central span of over half a mile, and a capacity of 12 railroad tracks, a roadway 150 feet wide, and four trolley lines.

Artist’s depiction of completed Hudson Bridge.

Better Highways Will Multiply Autos

By ALFRED REEVES, General Manager, National Automobile Chamber of Commerce.

WITHIN the next decade there may very possibly be 15,000,000 motor vehicles on the highways, some economists predict a larger number. This growth is likely to come gradually, as our highway systems develop and as city traffic conditions adapt themselves more fully to motor travel.

There will be an increase in the 3,000,000 cars now owned in rural districts, because the farmer cannot afford to be without a car.

The movement toward the suburbs manifest everywhere during the past 10 years will continue to be augmented through motor travel and in turn will increase the demand for automobiles.

Within the next decade there may very possibly be 15 million motor vehicles on the highways.

Where to Go and How to Get There

- This Map of Our Highways Tells You.

WILL you be one of the 10,000,000 tourists who will spend this summer’s holidays in the woodlands of Uncle Sam’s great national parks?

If so, you will want to know just how to get there—the most direct highways to follow and the camping places available along the route.

The map below, prepared by the American Automobile Association, will give you this information, picturing as it does the network of roads linking America’s playgrounds, as well as the convenient stops.

Four million tourists, statistics show, spent 10,000,000 vacation days in our national forests last year. The opening of new national pleasure grounds, and availability of ideal camping sites such as that shown at the left, will attract tourists in record numbers.

MAP: Where to Go and How to Get There. This Map of Our Highways Tells You. LARGER VERSION AVAILABLE - Click Button.
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Automobile camping in our national forests.

Our New National Parks Beckon Auto Campers

- Uncle Sam Opens Magnificent Playgrounds to Motor Vacationists.

KEEPING pace with the amazing increase in popularity of our national parks as summer play spots, Uncle Sam recently has opened remarkable new forest playgrounds for the pleasure of automobile vacationists and campers who will this summer ramble over the highways of the United States in unprecedented thousands.

No country in the world can boast such a variety of national parks with such varied scenery as the United States. Our latest acquisitions include our only national park in the East, embracing the only group of granite mountains on the Atlantic coast; the highest mountain in North America; the only active volcano in the United States proper; three volcanoes of world fame; a great and fascinating area in the Southwest, including the magnificent Zion National Park, still almost unknown territory to travelers; and finally the Grand Canyon National Park, popular for years, but only recently made a national park.

Two of these parks lie outside the United States proper—the Mount McKinley National Park in Alaska and the Hawaii National Park with three world-famous volcanoes. Many of them, however, are easily accessible to any family with an auto camping outfit, and can be visited the year round.

- The East’s New Playground

Of immediate interest to the greatest number of people is the new Lafayette National Park in Maine, the only national park in the eastern half of the United States.

Located on Mount Desert Island, near Bar Harbor, this forest playground is in the very heart of the summer resort section of seacoast America. The park itself embraces about 10,000 acres, half of this having been donated recently by private individuals.

There are rugged granite mountains, deep gorges, open meadows, seacoast and woodland—in fact, few places in America contain such a variety of scenery. There are 100 miles of trails through the park and a fine automobile road has been constructed around the island.

The present plan is to make the feature of this park the encouragement of water sports. Within a few years it is expected hundreds of vacationists will come here and live in houseboats for the summer, just as in other national parks they travel and camp by automobile. Since the waters surrounding the island are government waters, the problem is greatly simplified. Many attractive islands and inlets surrounding the park may gradually be added to its domain.

In the Southwest, land of the painted desert and the purple sage, two new national parks have recently been dedicated. One of these, the Grand Canyon National Park, has long been familiar to most persons simply as the Grand Canyon of the Colorado, but the Zion National Park, in southern Utah, is a new development that few have visited.

Here, on the south side of Mount McKinley, the new Alaska National Park, flow glaciers of great size, while on the north and west the mountain drops abruptly to grassy valleys. Mount McKinley rises 20,300 feet above sea level.
The view from Precipice Path in Lafayette National Park, Maine upper left, is one of rugged granite mountain sides and seacoast.
Far different are the gorgeous deserts of Bryce Canyon in Zion Park, Utah upper right . with its castle-like formations chiseled into sandstone and splashed with many colors.
This 500-foot suspension bridge across the Colorado is an important development in the Grand Canyon Park.

The most important development in connection with the Grand Canyon National Park has been the erection of a 500- foot suspension bridge across the Colorado River for the use of trail riders. This now makes it possible for one to visit both the north and south sides of the Grand Canyon, which was not possible in the old days, unless one rode in a car suspended from a cable, a nerve racking experience for the uninitiated.

The erection of this bridge is also important, since it means that one can visit Zion National Park, then cross and see both sides of the Grand Canyon.

- Uncle Sam Opens a New Park

Starting from the railroad station at Lund, Utah, within 20 miles of Zion National Park itself, one comes into view of the West Temple, a great red and white monument of natural stone, towering nearly a mile above the canyon floor. Giant sandstone cliffs with brilliantly contrasting colors make Zion Park a spot of rare beauty. These cliffs are often a bright red two thirds of the way up, with the summits topped off with white rock. Occasionally at the base are purple hues.

The new park contains approximately 120 square miles. The canyon of the Mukuntuweap River is about eight miles long, with walls rising to a height of 800 to 2000 feet on either side. Everywhere are these colossal monuments—the Vermilion Cliff joining the White Cliff, the Three Patriarchs, the Brown Wall, Angel’s Landing, and El Gobernador. El Gobernador is the remarkable monolith of the park, a great dome of red and white.

- Free Tourist Camping Ground

Zion National Park and the journey to and from it give one a vivid idea of the great desert country of the West. A free tourist camping ground is provided, as well as a more permanent camp where regular lodging and meals may be obtained.

If one desires to vary and extend his trip a little, he may visit Bryce Canyon, located to the northeast of Zion Park, and sometimes called the most gorgeous spectacle in the world. It is a canyon two miles wide by three miles long, cut 1000 feet deep in the plateau. All sorts of castle-like formations have been chiseled into the sandstone and splashed with nearly every color, including reds, tans, and purples.

“The Temple of the Sun,” seen in the distance, is one of nature’s colossal monuments in Zion Park.

As yet, few tourists have visited our Alaska national park, Mount McKinley, but with the completion of the railroad in that section more and more visitors will journey there in the summer. The park embraces the highest mountain in North America and will preserve at least a glimpse of primeval Alaska for posterity.

Mount McKinley rises 20,300 feet above sea level. On the north and west sides the mountain drops precipitately to grassy valleys with an altitude of only 3000 feet—a spectacle unequaled by any other mountain area in the world. From the other sides of the mountain flow glaciers of great size.

The wild animals are unusually abundant. There are herds of 1000 and 1500 caribou, or American reindeer, roaming the plateau. An ordinary day’s journey will show 500 or so mountain sheep, as well as moose and brown bear.

The last of our new national parks is the Lassen Volcanic National Park in California, for which Congress made its first appropriation only last year. Lassen Peak, with its altitude of 10,465 feet, is the only active volcano in the United States. The last violent eruption occurred in 1915. Hot springs and mud geysers may be seen.

The peak itself rises 5000 feet above the surrounding valleys. Eleven miles northeast is Cinder Cone, 600 feet from base to summit, and surrounding a crater 250 feet deep. Many volcanic bombs are strewn about. There is also the Devil’s Kitchen, a hillside and valley of mudpots and miniature mud volcanoes.

One enters the park from Chester, an attractive little village, which in turn is reached by automobile stage from Red Bluff or Chico.

With the completion of the Park-to-Park Highway, linking the national parks in the western half of the United States many American tourists have taken the family automobile and visited all of them in one season.

Nor would it seem out of the way that the United States should begin to attract foreign tourists to American parks in much the same way that Euro has sought American tourists in past years. Switzerland is often said to live on its scenery and Canada’s fourth income maker is also said to be her Scenery.

The United States might well divert international travel to its parks, and to some extent this is being accomplished.

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