Road signs and traffic signals

ROAD SIGNS

Road Signs:
Road signs are signs erected at the side of or above roads to give instructions or provide information to road users.  They are also called traffic signs. Various international conventions have helped to achieve a degree of uniformity in road signs in various countries. Traffic signs can be grouped into several types.  According to the Vienna Convention on Road Signs and Signals (1968), eight categories of signs have been defined which are listed below:
Danger warning signs
A warning sign is a type of sign which indicates a potential hazard, obstacle, or condition requiring special attention. Some are traffic signs that indicate hazards on roads that may not be readily apparent to a driver. They are normally indicated by an equilateral triangle with a white background and thick red border. Warning signs in some countries have a diamond shape in place of the standard triangular shape. The warning signs usually contain a symbol. Complex signage systems emerged with the appearance of motorcars. Initially, the use of four pictorial symbols, indicating bump, curve, intersection, and railroad crossing was agreed upon. Modern traffic warning signals can indicate any potential hazard, obstacle or condition requiring special attention. 

The following are the most common warning signs:
General caution

General warning signs are used in places where a particular hazard or condition is not covered by a standard sign. It is normally used to alert the driver regarding a potentially dangerous condition. It is normally indicated by an exclamation mark on a standard triangular sign

-Obstacles
Warning signs can be placed next to a specific obstacle

-Animals crossing the roadway
These signs warn of wild animals that may stray on to the road.

-Unusual vehicles in roadway
These signs are found where road users could encounter slow, large or non-typical vehicles. They are common around quarries, airports, industrial zones and rural areas

-Road work or construction
These signs are temporary in nature and road work, poor roads or temporary conditions on the road (flag men, survey crew, single-lane, detour, utility crew, blasting area, bump, dip, flooding, uneven pavement, freshly oiled road, loose gravel, smoke on road, trucks entering, etc).

-Curves and corners
Such signs indicate dangerous or unexpected bends on the road. Such signs indicate if curves are to the left or the right. They also indicate the angle of the curve and if it is a single curve or a series of curves.

-Chevrons and arrows
Chevron shaped symbols or arrows are placed at the actual location of the bend or curve to assist in negotiation of the curve.

-Tunnels
As the name suggests, these sign are used to indicate the presence of a tunnel ahead and may require the usage of headlights along with a change in light level. It naturally implies the presence of low ceiling clearance.

-Bridges
Traffic signs indicating the presence of a bridge might restrict trucks with a load limit for safety reasons

-Traffic signals
These signals indicate the presence of traffic lights ahead and warn the driver to prepare to slow down. They may be supplemented with a flashing light.

-Warning signs for regulatory signs
Sometimes, especially in dense areas where a sign has been added recently, some signs may be introduced for additional warning or reminder

-Intersections
These signs warn of road crossings.

-Lane starts and ends
These signs indicate when a multi-lane is being narrowed, or when a passing lane is ending, or where the road is widening or a passing lane is starting. Warning signs may also warn where a highway ends or where the road changes class or type

-Roads with one entry point
Such roads have only one entry or exit point. Such streets have a dead end or no outlet

-End of roadway
Such signs indicate the end of a roadway

-Pedestrian crossings
These signs are used to warn drivers of people walking in the street

-Schools
These signs mark school zones.

-Bicycle
These signs warn that bicycles will cross at that location

-Fire stations
These signs warn of firefighters enter the road with fire engines or other emergency apparatus. It is at these locations that other drivers will have to stop and let fire engines pass in case of an emergency

-Oncoming traffic
These signs are used to warn people of oncoming traffic when a road becomes a dual carriageway without a central median

-Level crossing (railway crossing)
Such signs warn of level crossings ahead. A red coloured warning sign with various pictograms is commonly used

-Falling rocks
These signs are used to indicate the hazards of fallen or falling rocks on the road ahead

-Road conditions
Such signs are used to indicate the state of the road ahead. For example - "slippery when wet", "grooved pavement", "open joints on bridge", "bump or dip ahead", etc.

B. Priority signs
Priority traffic signs indicate the order in which vehicles should pass intersection points.

Traffic Signals

Traffic lights, traffic signals, stoplights or robots are signalling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic.

Traffic lights follow a universal colour code which alternates the right of way accorded to users with a sequence of illuminating lamps or LEDs of three standard colours:

• Green light
  Allows traffic to proceed in the direction denoted, if it is safe to do so and there is room on the other side of the intersection.
• Red light
  Prohibits any traffic from proceeding. A flashing red indication requires traffic to stop and then proceed when safe (equivalent to a stop sign). 
• Amber light (also known as 'yellow light') warns that the signal is about to change to red, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so.

Before traffic lights, traffic police controlled the flow of traffic. An electric traffic light was developed in 1912 by Lester Wire, a policeman in Salt Lake City, Utah.  

Traffic lights (or traffic signals) are lights used to control the movement of traffic. They are placed on roads at intersections and crossings. The different colors of lights tell drivers what to do.

They help movement and help conduct an orderly flow by giving right of way to some cars and not others. They not only make car traffic a lot safer but also pedestrian traffic. 

They help reduce the number of accidents and make collisions at intersections a lot less frequent.

There are three main types of signal timing 

1. fixed timing, 
2. actuated timing, and 
3. coordinated timing. 

Fixed timing uses the same present time intervals that do not change in accordance to traffic volume.  

Actuated timing uses a detector that is able to adjust itself to different traffic volumes. 

Coordinated timing helps minimize starting and stopping at random which helps traffic flow and is less likely to create a traffic jam.

A traffic signal setup includes controller, traffic lights and detection. The controller works as the ‘brain’ of the entire setup and has the information that is required to make sure the lights work as per the required sequences. Traffic signals can run under a variety of different modes which can be dependent on location and time of day.  

There are 6 types of signals, viz- Traffic Control Signals, Fixed time signals, Manually operated signals, Traffic actuated (automatic) signals, Pedestrian signals, Special traffic signals.

Traffic signals should be placed so the signal heads are visible at a distance upstream of the intersection and from all lanes on the approach. Approaches with poorly placed traffic signals are likely to experience an increase of rear-end conflicts and collisions.