# Three keys to the study of road traffic: density, intensity and speed

## Three keys to the study of road traffic: density, intensity and speed

There are three key parameters when carrying out a road traffic study: density, intensity and speed. Vehicles circulating at a given time and on a particular road will be the keys to these three measurements.

To this end, all vehicles and their dimensions shall be taken into account: urban transport and public transport, trucks, cars, motorcycles, bicycles… At Ingartek we are specialists in road traffic studies. sustainable mobility is the handicap of any public transport administration, and at Ingartek we have a multidisciplinary team to analyze and provide the necessary solutions.

When the aim is to carry out a road traffic study, what data is obtained by analysing these three terms?

#### Density

We call traffic density the number of vehicles on a stretch of road at a given time. It is calculated based on speed and intensity measurements. The highest density will be when the section is full of vehicles in a row, with no gap between them; the length of vehicles is also taken into account. Under these conditions, vehicles are usually stationary and to calculate this maximum density a measurement of the length of the vehicles by the number of lanes will be made.

When carrying out mobility studies and analyzing road traffic by means of density, we will obtain data such as the quality of the traffic that will influence the speed of the vehicles, the number of manoeuvres to be carried out, the stops, the starts… Freedom of manoeuvre and separation between vehicles are the most valued aspects in terms of traffic quality.

#### Intensity

Measuring traffic intensity will help us to know the number of vehicles passing on a particular section of the road at a specific time: the hourly intensity will be measured by calculating the vehicles per hour and the daily intensity by calculating the vehicles per day. When analyzing traffic, intensity is the fundamental characteristic, since it will be the one that will allow us to characterize the type of traffic on a road section.

It is also necessary to take into account a law formed by a long-term trend, which has cyclical oscillations according to the year, week or day. On the one hand, there is the tourist nature of traffic, in annual cycles; and the proximity of a large population, usually on recreational trips. On the other hand, there is the concept of peak hour intensity; this characteristic is very interesting when measuring intensity.

#### Speed

Finally, speed is the third key: the relationship between the space traveled and the time spent traveling will be measured. It is expressed in km/h. However, there are other more precise concepts:

• Point velocity: speed of a vehicle passing through a section.
• Instantaneous speed: speed of a vehicle at a given time.
• Travel speed: average speed achieved on a section of road.
• Running speed: average speed discounting full stops.
• Average time speed: average speed of all vehicles passing through a particular location within a specified time period.
• Average spatial speed: the average speed of all vehicles that in an instant are on a particular stretch of road.
• Average travel speed: the average travel speed of all vehicles on a section of road.

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