Average speed monitoring

1.1 Composition and operating principle

Average speed monitoring zone consists of:
  • One or several average speed monitoring sections;
  • Server, which receives, and processes images and video footage captured by video units, located at the entrance and exit into each section of average speed monitoring zone.
Every section of average speed monitoring zone includes:
  • Section of road wih traffic moving in a single direction;
  • Video unit, located at the entrance into average speed control zone;
  • Video unit, located at the exit from average speed control zone.
Control zones of video units may be located both inside the average speed control section (Figure 1.1.), as well as outside of it (Figure 1.2.).
Figure 1.1 Average speed control section, video unit control zones inside the section
Figure 1.2 – Average speed control section, video unit control zones outside the section

1.2 Data storage and processing server

Data storage and processing server with “Average Speed” software module (number of licenses equal to number of average speed control sections), is set up according to the number of average speed control sections and is installed on the computer in data processing center (preferable) or on a computer of one of the control sections.

1.3 Calculating number of necessary average speed control sections

Set of equipment and number of necessary licenses are determined by number of average speed control sections. Number of average speed control sections is calclated taking into account the following:
  • Traffic in an average speed control section is moving in a single direction, control of reverse traffic flow requires an additional average speed control section;
  • Each average speed control section has only one speed limit;
  • Length of an average speed control section between entry and exit should not be less than 100 m. Closer placement of video units is not permitted.

1.3 Placing video units

Choosing the distance between video units

The system measures average speed of vehicles within specified metrological parameters only if the length of the control section, i.e. the distance travels, is no less than 100 m. Depending on the placement of video units at entrance and exit from average speed control section (direction of vehicle capture – through front or rear license plates), four correct placement options are possible, see Fig. 1.3. Attention: minimum distance of 100 m. IS NOT THE DISTANCE BETWEEN VIDEO UNITS! As seen from figures a), b) and d), if the distance between video units is 100 m, minimum length of an observed section is under 100 m, which is UNACCEPTABLE. To measure average speed on a given control section (and to record possible infractions), entrance and exit MUST be equipped with video units, capable to make timestamps linked to national UTC scale with a discrepancy not exceeding 1 ms.
a)
b)
c)
d)
Figure 1.3 – The distance between the video units depending on their direction

1.4.2 Average speed control zones, having sections with different speed limits

Each section of average speed control zone must have only ONE speed limit. For example, road section has two speed limits – 90 km/h and 60 km/h, which would require division of a zone into two control sections (one with 90 km/h speed limit, second with 60 km/h speed limit), Figure 1.4 (1 – recognition unit, 2 – observation unit).
Figure 1.4 – Average speed control zones, having sections with different speed limits
Nevertheless, it is possible to use exit line of one average speed control section as an entrance line to the next control section. Example: the exit of the average speed control zone 1 (Boundary 2) is used as an entrance to the average speed control zone 2, and the exit from the average speed control zone 2 (Boundary 3) is used as an entrance to the average speed control zone 3 (Figure 1.4). For road sections with different speed limits, it is necessary to place video units relative to the movement of vehicles so that the average speed control section with a lower average speed limit contains the video unit control zone, see Figure 1.1, and the average speed control section with a higher average speed limit does not contain video unit control zones, see Figure 1.2, Example: The average speed control section 1 and the average speed control section 3 with a maximum limit of 60 km/h contain a video unit control zone, and the average speed control section 2 with a maximum limit of 90 km/h does not contain a control zone.

1.4.3 Control of two traffic directions

If a control zone of video units at the entrance and exit from the road section captures both traffic directions, as shown on Figure 1.5, then you need to configure two sections of average speed control – separately for each direction.
Figure 1.5 – Control of two traffic directions

1.4.4 Control of broad road sections

If the road section is wide (has several control zones), then it is necessary to set up such a number of average speed control sections that will cover all possible ways a vehicle may to travel through control zones at the entrance and exit of this wide road section. For example, for a section of road with four lanes, where two recognition units are installed to control the entire width of the road, as Figure 1.6 shows, you need to configure four average speed control sections that pair each video sensor at the entrance to each unit at the exit:
  • Average speed control section No. 1 (video units 1-2);
  • Average speed control section No. 2 (video units 1-3);
  • Average speed control section No. 3 (video units 4-2);
  • Average speed control section No. 4 (video units 4-3).
Figure 1.6 – Intersecting average speed control sections

1.5 Recording infractions

1.5.1 Exceeding prescribed average speed

The average speed measurement is based on an indirect measurement method – independent measurements are made of the path traveled by a vehicle between video unit control zones at the entrance and exit to the average speed control section, and the time from the moment the vehicle is captured by a video unit in the control zone at the entrance to the moment the vehicle is captured by video unit of a control zone at the exit from the average speed control section.
  • Measurement of the path traveled by a vehicle between control zones of video units consists of three stages, see Figure 1.7:
  • measurement of the path in the control zone of a video unit at the entrance to the average speed control section;
  • measurement of the path in the control zone of a video unit at the exit to the average speed control section;
  • calculation of the total distance traveled by a particular vehicle, taking into account the distance between video units at the entrance and exit (following actual profile of the road, taking into account elevations and turns, as measured during calibration of the System) and the measured distances in control zones of video units at the entry and exit.
The time that a vehicle spent traveling through average speed control section is calculated as the difference between the recording time by a video unit at the exit and the recording time by a video unit at an entrance to the average speed control section.
Figure 1.7 – Calculating a vehicle path through average speed control section
Average speed of a vehicle in an average speed control section is calculated according to the formula: where V – desired average speed of a vehicle; S – Distance travelled by a vehicle between control zones of video units at an entrance and exit; T – time, which a vehicle spent on travel.

1.5.2 Not following requirements set forth by road signs and markings

To capture a crossing of a solid road marking line, as shown on Figure 1.8, it is necessary to determine traffic lanes at entrance and exit to the section. In software settings of control areas for each lane, certain portion of the road is designated in each control zone, and, if a vehicle is in different areas at entry and exit, it is assumed that it has crossed the road marking line.
Figure 1.8 – Capturing a crossing of a solid road marking line