There are two different approaches to represent speed Studies. **1) Spot Speed** **2) Average speed**.

**2) Average speed-** There are two types of average speed.

a) Time mean speed

b) Space mean speed

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**Spot Speed**

It is the instantaneous speed of a vehicle. It can be measured using an Endoscope, Loop deflector, and Pressure contact tubes.

Spot speed statistics refers back to the dimension of individual speeds of cars passing a point on a roadway.Care needs to be taken to behavior the have a look at accurately so that the pattern statistics will adequately mirror the velocity characteristics of the population.

Spot speed studies are used to decide the rate distribution of a traffic movement at a selected location. The information accumulated in spot velocity studies is used to decide car velocity percentiles, which might be beneficial in making many velocity-related decisions. Spot Speed: Speed is a critical measure of the quality of travel and protection of street networks. Speed through definition is the rate of motion of the car in distance in keeping with the unit time. A usual unit of velocity in kilometers per hour (kph) or miles per hour (mph). Basically, **there are two types of speed:**

### 1. Time-mean speed

1. time-mean speed is the average spot speed of several vehicles measured at a given spot.

It is the arithmetic mean of the speed of vehicles passing a point on a highway during an interval of time.

Where

is time mean speed in kmph

Vi is observed instantaneous speed of ith vehicles in kmph

n is the number of vehicles observed

Note – when speed is given in the form of various speed range then

Where

qi is no of vehicles in ith speed range

Vi is the mean velocity of vehicles the speed range

### 2. Space-mean speed

2. space-mean speed is the length of a road section divided by the average travel time of several vehicles over this specific section. spot speed time-mean speed space-mean speed.

It is the harmonic mean of the speed of vehicles over a certain road length at any time.

Time mean speed = [/Latex] \frac{\sum_{ }q_i\:} {\sum {\frac{q_i}{V_i}}} [Latex]

Where

qi is no of vehicles in an ith speed range

Vi is the mean velocity of vehicles the speed range

### Typical purposes of speed studies

Speed trends over time | |

Traffic control planning | |

Before-and-after studies | |

Crash analysis | |

Geometric design | |

Research studies |

During the period of the national maximum velocity limit, states monitored speeds on their roads on a periodic foundation Speed information are wanted for traffic signal warrant analysis, and for making plans residential location traffic control Before-and-after velocity studies are undertaken to decide if modifications in roadway design or operation have altered car speeds Speed may make contributions to crash frequency and it surely contributes to crash severity. Speed studies can be carried out at high accident locations; however, a locating of higher speeds at this type of spot does now no longer mean that the speeds of real crash-worried vehicles are high Note that speed laws, measurements, and published limits withinside the US are expressed in mph. The notes and those visible aids follow this practice. For conversion purposes, 1 mph = 1 km/h.

## Speed characteristics from a spot speed study may be used to

- Establish parameters for traffic operation and management, which include speed zones, velocity restriction (85th percentile velocity is normally used as the rate limit on a road), and passing restriction.
- Evaluate the effectiveness of traffic management devices, which include variable message signs at work zones.
- Monitor the impact of velocity enforcement programs which includes using drone radar and using differential velocity limits for passenger Vehicle
- Evaluate and or determine the adequacy of highway geometric characteristics which includes radii of horizontal curves and lengths of vertical curves
- Evaluate the impact of velocity on highway protection through the analysis of crash statistics for different velocity characteristics Determine velocity trends
- Determine whether complaints about speeding are valid.

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