Traffic History Archives

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Traffic Lights Invented by William L. Potts

The Inventor of the Traffic Light William L. Potts

Traffic Light Definition: A road signal for directing vehicular traffic by means of colored lights, typically red for stop, green for go, and yellow for proceed with caution.

At a Glance:

traffic light GIFPolice Officer William L. Potts of Detroit, Michigan, decided to do something about the problem caused by the ever increasing number of automobiles on the streets. What he had in mind was figuring out a way to adapt railroad signals for street use. Potts used red, amber, and green railroad lights and about thirty-seven dollars worth of wire and electrical controls to make the world’s first 4-way three color traffic light. It was installed in 1920 on the corner of Woodward and Michigan Avenues in Detroit. Within a year, Detroit had installed a total of fifteen of the new automatic lights.

The Story:
Even during the horse and buggy days, traffic in big cities was often heavy. Police officers had to be stationed full time directing traffic at busy intersections.

The world’s first traffic light came into being before the automobile was in use, and traffic consisted only of pedestrians, buggies, and wagons.  Installed at an intersection in London in 1868, it was a revolving lantern with red and green signals.  Red meant “stop” and green meant “caution.”  The lantern, illuminated by gas, was turned by means of a lever at its base so that the appropriate light faced traffic.  On January 2, 1869, this crude traffic light exploded, injuring the policeman who was operating it.

With the coming of automobiles, the situation got even worse. Police Officer William L.  Potts of Detroit, Michigan, decided to do something about the problem.  What he had in mind was figuring out a way to adapt railroad signals for street use.  The railroads were already utilizing automatic controls. But railroad traffic traveled along parallel lines.  Street traffic traveled at right angles. Potts used red, amber, and green railroad lights and about thirty-seven dollars worth of wire and electrical controls to make the world’s first 4-way three color traffic light. It was installed in 1920 on the corner of Woodward and Michigan Avenues in Detroit. Within a year, Detroit had installed a total of fifteen of the new automatic lights.

At about the same time, Garrett Morgan of Cleveland, Ohio realized the need to control the flow of traffic. A gifted inventor and reportedly the first African American to own an automobile in Cleveland, Ohio, he invented the electric automatic traffic light. Though it looked more like the semaphore signals you see at train crossings today.

Many others had obtained US Patents for Traffic Signals, some as early as 1918. But Morgan’s Patent was purchased by General Electric Corporation and provided the protection they needed to begin building a monopoly on traffic light manufacture.

worlds first signal tower traffic light signal

The first signal tower with automatic lights, at Michigan and Woodward

Fun Facts:

The Morgan traffic signal was a T-shaped pole unit that featured three positions: Stop, Go and an all-directional stop position. This “third position” halted traffic in all directions to allow pedestrians to cross streets more safely.traffic signal light GIF

Morgan’s traffic management device was used throughout North America until it was replaced by the red, yellow and green-light traffic signals currently used around the world.

Morganr sold the rights to his traffic signal to the General Electric Corporation for $40,000.

Shortly before his death, in 1963, Morgan was awarded a citation for his traffic signal by the United States Government.

Garrett Morgan earned US Patent No.1,475,024 issued November 20, 1923 fot his traffic signal

Traffic Sign History

gallery of interstate highway signs from different states

The History of United States Highway Signs

U.S. Numbered Highways have used the same basic shield since before the numbering scheme was agreed upon.
1925: The preliminary design was first proposed April 20, 1925, the same day the Joint Board on Interstate Highways decided that a numbering system would be preferable to names. Leo Boulay of Ohio suggested using the official United States shield and the designation ‘U.S.A.’. The shield had been in use by the U.S. government in various forms since the late 1700’s and a version of it can be found on modern American currency. Automobile Blue Books, Inc. of Chicago, Illinois used a blue variant of the US shield with white lettering to endorse Hotels, Garages, Restaurants, Tea Rooms, and Inns in the 1920’s.

The first plan was to use the basic shape of the official US shield as the route marker with the addition of “U.S.A.” and a route number. An early debate on color schemes was between yellow with black numbers and white with black numbers. Yellow offered better winter and snow visibility, but the color was also being proposed for use with several other road signs at the time, all related to road hazards. The color white was decided upon for the US shield.

 The first US shield actually fabricated as an example was the then-unused number ’56’ with the state of Maine . The final choice of design for the US Highway shield in 1926 was a design by Mr. Frank Cnare, who worked for the Wisconsin State Highway Dept. Mr. Cnare has a flair for drawing, and his design beat out the other 48 states hands down. His design used the U.S.D.A. logo in a very tasteful way that appealed to them very much.

Late 1920’s – Mid 1940’s: In “American Highways” April 1927, Vol. VI No. 2, the sign approved for the US numbered highway system was described thusly: “The design adopted is the commonly known United States shield outline, and this shield carries the route number, as well as the State name through which the road passes.” The chosen size for the US highway shields was approximately 18″ x 18″. US Markers in the early days were made of 16 gauge heavy embossed steel (although some states did use very heavy cast iron in place of the steel). This sign featured the state name on the top cavity, and “US” and the highway number on the bottom.

Early US signs were supposed to be all in block letters, but some curves snuck in, like the ‘S’ in the old US 66 signs. The first US shields posted in 1926 and 1927 indicated left and right turns in the numbered route by R’s and L’s in smaller US shields. Many states kept to a similar practice into the 1930’s,.

“City” U.S. Highway Shields: There was a second type of early US shield, approved for ‘city’ use. It was smaller, at around eleven inches high and wide. The smaller city-use signs dropped the state name, and only placed US in the banner area that was formerly reserved for the state name. Bannered US routes started coming into wide usage after the September 1934 AASHO meeting. Prior to that, a suffix of T had been used to denote Temporary routes, a designation that continues to be acceptable to this day as TEMP. Auxillary banner signs for road types did not come into wide use until the 1960’s.

Mid 1940’s – Mid 1950’s: In the 1943 Ohio MUTCD, they recommended the use of the “M-101” which was an outline of a US Marker on a white background, using a square sign instead of the traditonal cut-out shields. This subsequently was carried over into the National 1948 MUTCD, which changed the use of the embossed “squared off” lettering and numerals. They recommended the use at junctions and turns. In 1950 a new design was introduced by Illinois that featured the state name across the top, a divider line on a 16″ x 16″ cutout, and removing the “US” and using larger numerals on the sign. In 1953, AASHO put their foot down and required the “US” be placed back on the signs. This lead to yet another design change in 1954, when Ohio, and many of the eastern states decided to place an abbreviation and the US on the top line of the sign and remove the divider line. Examples were “OHIO-US”, “MASS-US, “CONN-US, “D.C.-US”, “MISS-US”, “TENN-US” etc. By way of contrast, both the Carolinas went as far as to spell out “UNITED STATES” using series “A” on the top of their signs, however, this design was very short lived as well, because series “A” is very hard to read.

Mid 1950’s: In the 1950’s, a new Manual of Uniform Traffic Control Devices (MUTCD) changed the approved color for stop signs from black lettering on a yellow background to the now-familiar red background with white lettering. It apparently also authorized dropping the in-shield bannering, leaving just a number inside the US shield shape. Colors were not directly specified. Some states took the opportunity to change the color of the US highway shield as well. Washington, D.C. experimented with this in 1952. The state of Florida went the furthest with this idea, and started color-coding all its US shields in 1956. This resulted in odd colors like orange for US 41 and yellow for US 301. FHWA was and still is is willing to let FDOT post colored US shields, as long as it is all Florida funded. Any US shield placed with the asistance of federally collected gas tax money must conform to the most recent MUTCD. Throughout the 1980’s, FDOT maintenance crews replaced new black on white US signs on new projects with FDOT color scheme equivalents. FDOT finally decided the expense of the experiment was too great, and ceased making new colored US shields August 12, 1993. New and replaced US highway signs are the standard black numbers on white background. Vesitiges of the old coloring scheme remain, primarily in urban areas.

Kansas experimented with a new color, green, on the newly assigned US 56. Arizona experimented with directional coloring in the 1950’s and 1960’s. Mississippi colored some shields in a scheme similar to Florida’s, but possibly only in cities. Washington State experimented with directional-colored US shields in urban areas in the 1950’s. Rhode Island reportedly experimented with a red and white US 1 sign like Florida’s. Wisconsin also utilized colored US signs, Business / City US signs were yellow .
Another interesting design for US Route Markers was used in the state of Texas from 1954 – 1968. They used a standard 20″ x 20″ size marker and a larger 24″ x 24″ size marker where greater visibility was required. However, the most unique feature of their signs was the direction, turn, and trailblazer, 24″ x 24″ size markers they used. The signs were laid out with the “US” across the top, a divider line, then the numerals. Beside the numerals were a variety of arrows to indicate directions and turns of the route, or how to reach it.
old historic route 66 highway signs

Today: The states of California and Virginia still use cut-out US shields, as opposed to the standard approved black square with a white shield. California even places US on some shields. The six point US highway shield is still the highly recognizable symbol of the road system that binds the country together, from doorstop to doorstop. US 66 was decommissioned in 1985. There has been such a demand to follow the old route between Chicago and Los Angeles that “Historic US 66” brown and white US type shields are being posted in increasing numbers. The affection for the old road along the interstate is such that the states along the route have to protect the remaining original US shields from souvenir hunters and collectors. Arizona had a brief problem with the new “Historic US 66” being stolen. Legally, US Route 66 may have been decommissioned, but it has stayed in the hearts of those who lived and worked along its mostly two-lane alignment, and it stayed in the conciousness of America. The familiar US shield shape is even being painted on the asphalt in some areas of Old 66. Today the State of California is also using a modified US shield to unofficially bring back US 99 and sections of US 101 decommissioned in 1964. Arizona decomissioned or truncated many US routes in 1993, then reposted brown “Historic” shields on sections a few years later. The success of the use of green in Interstate business routes has led to the posting of a few US business routes with green shields.

Images of Old Gas Stations

The Firsts in the History of World Traffic

first car crash in the world 

The First Accident

In 1771 the first accident involving a motor vehicle took place in Paris when Cugnot’s steam tractor hit a low wall in the grounds of the Paris arsenal.

The Highway First Act

The Locomotives and Highway Act was the first piece of British motoring legislation. This was also known as the Red Flag Act of 1865. The act required three persons in attendance one to steer, one to stoke and one to walk 60 yards ahead with a red flag to warn the oncoming traffic.

The First License Plate of the World

The world’s first car number plates were issued by the French police in 1893.

First Man to get a traffic ticket

In 1895 John Henry Knight was convicted and fined for using a motor-tricycle on the highway. He was probably the first motorist to appear in court.

First Fatal Car Accident

The first motor-car accident in Britain resulting in the death of the driver occurred in Grove Hill, Harrow-on-the Hill, London, on 25th February 1899.

The First Dusty Road to Tar Surface

In 1902 Tar was first used on a Macadam surface to prevent dust in Monte Carlo. It was the idea of Dr. Guglielminetti, a Swiss. At first the tar was brushed in cold, but soon it was applied hot.

The Motor Car Act

The Motor Car Act of Britain came into force on 1st January 1904. It required that all cars be registered and carry a number plate, and all motorists to have a driving licence. But there was no driving test to pass and the licence was obtained by filing up a form and paying the fee at a post office. The act made dangerous driving an indictable offence.

The First Gas Pump

The first petrol pump was installed in USA in 1906.

The First Traffic Light of the World

The World’s first traffic lights were installed in Detroit, USA in 1919. The first traffic lights in Britain were installed in Wolverhampton during 1928. However, they did not come to London till 1932.

First Pedestrian Crossing

The pedestrian crossing were instituted in Britain in 1934. The roads were marked by dotted lines. On the pavement there were striped Belisha beacon light poles named after Britain’s Minister of Transport L. Hore-Belisha. The Zebra crossing with black and white stripes was developed after the second world war.

 First Traffic Police Woman

Police women were used for traffic control duties for the first time in Paris in 1964. In Delhi we introduced women traffic police in 1989.

First Box Junction

Box junctions, marked with yellow cross-hatching, were introduced in London during 1964. The aim was to prevent traffic blocking junctions when it could not proceed and this was successful