How Traffic Light Systems Work

Gone are the horse and buggy days. Nevertheless, the sad part is that we still do not notice the endless number of traffic signals. Who are the inventors of these signal lights? What makes a traffic light work? These interesting facts make up this article!

Introduction

Urbanization has brought rapid development in industries due to which the majority of the population is settling down in the cities. This results in a heavy rush in vehicular traffic requiring efficient control to avoid accidents. Traffic lights can be seen arranged one above the other at crucial crossings and junctions in a city. The colors used for traffic lights are green, yellow, and red, out of which red denotes stop, green is used to indicate ‘carry on,’ and the yellow color is used in between to be ready for either red or green.

Lights changes are either preset with a timer or based on current conditions and connected with one another in such a way that traffic can move on the main road controlling their speed. However, these days the interval between traffic lights is computerized and not set. They change, but vary in sync with vehicular traffic.

History of traffic lights

The question of traffic safety existed even before automobiles were used. This led to the invention of the world's first traffic light in London in 1868. A revolving lantern comprising of red and green signals was set up at a junction in London. These lights were lit with the help of gas and operated by men. A lever at the base of the light was used to turn the colors of the light and allow the traffic to flow. Regrettably, in January 1869, this piece of equipment blew out and hurt the police officer who was controlling it at the time.

The contemporary red and green electric traffic light was invented in 1912 by a Utah police officer named Lester Wire. In 1914, the first traffic signal was installed in Cleveland, Ohio. This device had a buzzer apart from the normal red and green colors. The buzzer was used to provide a warning of the color changes. This device was designed by James Hoge and was used by both the police and the fire stations to manage the signals in an emergency. Police officer William Potts invented the first four-way, three-color traffic light in 1920.

The first coordinated traffic signal arrangement system was set up in 1917 and had six linked points of intersections operated concurrently by a manual switch. In 1922 in Houston, Texas control of the interconnected lights was done automatically. Inter-linked traffic lights with automatic control were introduced in Wolverhampton, England only in 1927.

Traffic lights

Color Code for traffic signal lights

All of us know that red, green and yellow are used as traffic light signals. Why were these colors selected?

The rules which governed the right of way in maritime to recognize port was red and starboard was green, which signaled that the vessel on the left had to stop to allow the one on the right to cross.

Actually, the colors for traffic lights were adopted from the color code used by railway engineers as a traffic signal invented to control the trains on the rail lines. They used red to represent a signal to stop since it represents danger or warning and this color caught the attention of passersby as well. The other two colors used by railway engineers were green symbolizing ‘caution’ and white meaning ‘go.’ Filters were used in traffic signals and because of this the white color had some problems associated with it. Streetlights, stars, and the glare of sunlight or other lights could be misunderstood as a ‘go’ signal since they also shone as white from a distance. In order to solve this problem engineers used yellow to denote caution.

Working Mechanism of Traffic Lights

In olden times, the change in color of traffic lights was preset with fixed timings. This means that when a vehicle draws up exactly as the signal alters from green to red, it has to wait for the next change to green, even if there are no other vehicles in any other directions.

Yet the contemporary style consists of signals that are not fixed, but act in response to the presence of vehicles. This system uses a sensor loop embedded in the pavement that detects weak magnetic fields such as the metallic parts of cars. A controller box installed nearby contains a computer that senses the vehicle’s presence. If no other cars are found waiting, the controller blinks the green signal.

The waiting vehicle then moves on. If a centrally computerized traffic arrangement is installed, then a set of lights can be controlled concurrently allowing smooth passage of traffic.

New Research (Adaptive Traffic Lights)

Traffic lights acting locally will better the control of traffic globally, and this is the new research going on at present. With regard to adaptive traffic lights, a mechanical engineer, Gábor Orosz of the University of Michigan says, “It’s very interesting- the approach is adaptive and the system can react. That’s how it should be- that’s how we can get the most out of our current system."

The Portland Cement Manufacturing Process

Most of the time you see Portland cement used for construction. This article will explain the Portland cement manufacturing process in its simplest form.

From the construction of buildings to bridges, airports to over-passes, the applications for Portland cement are enormous. So are the requirements of different types of Portland cement. Though the proportion of the various ingredients may vary for different cement manufacturers, the cement manufacturing process at the basic level remains the same.

Different Steps for Portland Cement Manufacturing Process

Collecting the Ingredients: Lime, silica and alumina are the three basic ingredients of cement. The source of the lime is limestone. Silica is obtained from clay, and alumina is obtained from bauxite.

Grinding the Ingredients: The ingredients are grinded to make them small enough to pass a sieve of size 200. The grounded ingredients are then mixed homogeneously.

Making Clinkers: The grinded mixture is then fed into a inclined tubular kiln for roasting. Temperature of this roasting kiln is around 1500 to 1700 degree centigrade. During the process of roasting, Silica, alumina and lime are converted into calcium aluminates. The ingredients take the shape of small lumps called clinker.

Cooling the Clinkers: The hot clinkers cannot be used directly for the further processing. The clinkers are stored for cooling to a temperature of 50 to 55 degree centigrade.

Grinding the Clinkers: The clinkers then need to be finely grinded to make cement. While grinding, 2 to 5 percent gypsum to be added. Gypsum retards the setting time of the cement upon mixing it with water.

Storage and Packing: The cement is then stored in large silos until weighing and packing. Packed cement is then supplied to market.

Conclusion

Portland cement manufacturing is a large scale process. The quality of the final manufactured cement depends upon the proportion of the ingredient and maintaining proper process parameters. To ensure the end quality, a strict quality check is maintained throughout the entire Portland cement manufacturing process.