Summary of Speed Indicator Device (SID) Activity
For the Period 18th January to 11th February 2021
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Location : During this period the SID was positioned on the A 354 Salisbury Road at the East end of the village, which is in a 40 mph speed limit zone. The SID was mounted on a fixed signpost on the left-hand side of the road as you leave Coombe Bissett village heading towards Salisbury. This site is referred to as the Area 1 Secondary site.
For more information regarding approved SID sites in Coombe Bissett and Homington villages please refer to the SID location Power Point guide.
For more information regarding approved SID sites in Coombe Bissett and Homington villages please refer to the SID location Power Point guide.
Detailed PDF reports:
Please refer to the tab for Salisbury Road for more detailed analysis of traffic data recorded by the SID, which is presented in PDF report format. Guidance Notes to each section of the PDF reports are provided below this summary.
Note: Our SID does not have GPS and therefore its reports are location agnostic. References in reports to Incoming and Outgoing traffic refer to traffic coming towards the device (Incoming) and traffic going past the device in the opposite direction (Outgoing).
Please refer to the tab for Salisbury Road for more detailed analysis of traffic data recorded by the SID, which is presented in PDF report format. Guidance Notes to each section of the PDF reports are provided below this summary.
Note: Our SID does not have GPS and therefore its reports are location agnostic. References in reports to Incoming and Outgoing traffic refer to traffic coming towards the device (Incoming) and traffic going past the device in the opposite direction (Outgoing).
While the Coombe Bissett Community Speed Watch (CSW) remains suspended for the duration of the current Lockdown, we have been notified by Wiltshire CSW in Trowbridge that we can resume speed checks with effect from 29th March 2021.
NOTE EXPLAINING INFORMATION IN PDF REPORTS
OF SPEED INDICATOR DEVICE (SID) ACTIVITY
COVER PAGE
The start and end dates for the period the device has been active at a location are shown on all pages.
Location: Records where the SID device was positioned during the report period and is shown on all pages.
Note: The Parish Council agreed that the SID should serve as much of the community as possible. Sites have had to be agreed by Wiltshire Council. At present there are a total of 7 approved sites. Details of exactly where each site is located are available in a separate document.
Comments: Details here show the speed limit for the site where the SID was located and the direction of traffic the SID was monitoring at that location:
- Inbound relates to traffic coming into the village
- Outbound relates to traffic leaving the village
The Comments section also states whether the sign was actively displaying the speed information to oncoming traffic or if it was in ‘Spy Mode’. Spy Mode records traffic information but does not display speeds, and is used to baseline traffic speeds at the start of the period.
PAGE TWO: AVERAGE SPEEDS
The Average Speeds graph includes two averages:
- An ‘average by time period’, which is displayed as a curve on the graph. (one curve per direction: ingoing/outgoing).
- An overall average which is displayed as a numeric value just below the graph.
The ‘average by time period’ corresponds to the arithmetic average calculated on the speeds recorded between the start/end dates. They are presented on a default time period of 30 minutes. The overall average corresponds to the arithmetic average of all the speeds included between the starting/ending dates on the time period selected for the PDF report. The software sums up all of the recorded speeds, then divides the result by the number of vehicles measured.
Note: References in the PDF report to Incoming direction and Outgoing direction relate to the direction of traffic in relation to the SID. ‘Incoming’ relates to traffic heading towards the device. ‘Outgoing’ relates to traffic going past the device in the opposite direction
PAGE THREE: MAXIMUM SPEEDS
Similar to the information for average speeds, the graphs relating to maximum speeds are displayed in curve and number format.
- The maximum speed recorded per time period are displayed in graph form (oncoming and outgoing are reflected in different colours).
- The maximum speed recorded over the entire time period is shown for each direction as a numeric value just below the graph.
PAGE FOUR: VEHICLES PER HOUR
Graphs show traffic volumes for incoming traffic (Green) and outgoing traffic (Blue) for each 24-hour period covered by the report. Total volumes are shown at the top right of the graph
PAGE FIVE: SPEED DISTRIBUTION FOR INCOMING TRAFFIC
PAGE SIX: SPEED DISTRIBUTION FOR OUTGOING TRAFFIC
In these sections, the recorded speeds are represented in pie chart form, and allow you to see the percentage of vehicles which have, or have not, observed the speed limit.
The first segment shows the percentage of vehicles which are travelling below or at the legal speed limit in that location. The second segment shows the percentage of vehicles which are travelling above the legal limit but approximately within the speed tolerances permitted by Wiltshire Police and Community Speed Watch before drivers may be sanctioned. The remaining segments show the percentage of vehicles travelling at excessive speeds.
PAGE SEVEN: PERCENTILES FOR INCOMING TRAFFIC
PAGE EIGHT: PERCENTILES FOR OUTGOING TRAFFIC
The 85th percentile is an indicator that helps illustrate the behaviour of the majority of drivers. It reflects the speed respected by 85% of motorists and is obtained by stripping out the bottom and top & bottom 7.5% of speeds recorded (i.e. strips out the extremely fast and extremely slow vehicles).
If the 85% threshold is close to the average speed recorded, this indicates that the speeds observed on a road are consistent. If it is not close to the average speed, this means that a significant proportion of drivers are above the average recorded speed.
Note: Wiltshire Police use 85th Percentile speeds to determine whether they should conduct their own Speed Checks in any location. This is normally determined by the use of a Traffic Speed Survey which is sometimes referred to as a Metro Count. It involves two rubber strips placed across the road connected to a recording device. To-date, the Parish Council have had to request Speed Traffic Survey reports on a case by case basis, before any Police enforcement action will be considered.
The start and end dates for the period the device has been active at a location are shown on all pages.
Location: Records where the SID device was positioned during the report period and is shown on all pages.
Note: The Parish Council agreed that the SID should serve as much of the community as possible. Sites have had to be agreed by Wiltshire Council. At present there are a total of 7 approved sites. Details of exactly where each site is located are available in a separate document.
Comments: Details here show the speed limit for the site where the SID was located and the direction of traffic the SID was monitoring at that location:
- Inbound relates to traffic coming into the village
- Outbound relates to traffic leaving the village
The Comments section also states whether the sign was actively displaying the speed information to oncoming traffic or if it was in ‘Spy Mode’. Spy Mode records traffic information but does not display speeds, and is used to baseline traffic speeds at the start of the period.
PAGE TWO: AVERAGE SPEEDS
The Average Speeds graph includes two averages:
- An ‘average by time period’, which is displayed as a curve on the graph. (one curve per direction: ingoing/outgoing).
- An overall average which is displayed as a numeric value just below the graph.
The ‘average by time period’ corresponds to the arithmetic average calculated on the speeds recorded between the start/end dates. They are presented on a default time period of 30 minutes. The overall average corresponds to the arithmetic average of all the speeds included between the starting/ending dates on the time period selected for the PDF report. The software sums up all of the recorded speeds, then divides the result by the number of vehicles measured.
Note: References in the PDF report to Incoming direction and Outgoing direction relate to the direction of traffic in relation to the SID. ‘Incoming’ relates to traffic heading towards the device. ‘Outgoing’ relates to traffic going past the device in the opposite direction
PAGE THREE: MAXIMUM SPEEDS
Similar to the information for average speeds, the graphs relating to maximum speeds are displayed in curve and number format.
- The maximum speed recorded per time period are displayed in graph form (oncoming and outgoing are reflected in different colours).
- The maximum speed recorded over the entire time period is shown for each direction as a numeric value just below the graph.
PAGE FOUR: VEHICLES PER HOUR
Graphs show traffic volumes for incoming traffic (Green) and outgoing traffic (Blue) for each 24-hour period covered by the report. Total volumes are shown at the top right of the graph
PAGE FIVE: SPEED DISTRIBUTION FOR INCOMING TRAFFIC
PAGE SIX: SPEED DISTRIBUTION FOR OUTGOING TRAFFIC
In these sections, the recorded speeds are represented in pie chart form, and allow you to see the percentage of vehicles which have, or have not, observed the speed limit.
The first segment shows the percentage of vehicles which are travelling below or at the legal speed limit in that location. The second segment shows the percentage of vehicles which are travelling above the legal limit but approximately within the speed tolerances permitted by Wiltshire Police and Community Speed Watch before drivers may be sanctioned. The remaining segments show the percentage of vehicles travelling at excessive speeds.
PAGE SEVEN: PERCENTILES FOR INCOMING TRAFFIC
PAGE EIGHT: PERCENTILES FOR OUTGOING TRAFFIC
The 85th percentile is an indicator that helps illustrate the behaviour of the majority of drivers. It reflects the speed respected by 85% of motorists and is obtained by stripping out the bottom and top & bottom 7.5% of speeds recorded (i.e. strips out the extremely fast and extremely slow vehicles).
If the 85% threshold is close to the average speed recorded, this indicates that the speeds observed on a road are consistent. If it is not close to the average speed, this means that a significant proportion of drivers are above the average recorded speed.
Note: Wiltshire Police use 85th Percentile speeds to determine whether they should conduct their own Speed Checks in any location. This is normally determined by the use of a Traffic Speed Survey which is sometimes referred to as a Metro Count. It involves two rubber strips placed across the road connected to a recording device. To-date, the Parish Council have had to request Speed Traffic Survey reports on a case by case basis, before any Police enforcement action will be considered.
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