Independent traffic analysis methodology
A wide range of factors beyond the LTNs themselves influence traffic patterns across a wider area and the time frame over which we would expect to see traffic levels reducing. These factors include street works, bridge closures, changes by neighbouring boroughs/Transport for London and evolving Covid-19 related restrictions at the London and national scale. These factors must be analysed to understand the specific benefits and impacts of an LTN.
- Using data from before the LTN was introduced and traffic data through the Covid-19 pandemic we will be monitoring a range of before and after data sets to assess the impact of our new schemes.
- Data will be collected inside LTN areas as well as on the immediate boundary roads that surround an LTN area for the 3 assessment stages.
- This data will be compared with our initial baseline and calibrated against travel trends in the wider London area to understand the effect of the LTN in its wider practical context to see if traffic levels have:
- reduced within the LTN area
- reduced across the area, when considering boundary roads and the inner LTN area together
Traffic data collected will differ according to the monitoring stage and includes:
• traffic counts – Stage 1,2,3
• traffic speeds – Stage 2,3
• ANPR camera compliance levels – Stage 2,3
• vehicle journey times - Stage 2,3
• bus journey times – Stage 2,3
• emergency service response times – Stage 2,3
Monitoring of the LTNs is being completed by independent transport consultancies as follows:
- SYSTRA leading on the monitoring programme and coordinating the independent traffic analysis
- MHTC leading on the Automatic Traffic Counts (ATC) data collection
- The Floow leading on the telematic data collection and analysis
- Project Centre validating the traffic survey data analysis completed by SYSTRA
Full analysis, methodology and summary details for each count location can be found in the Independent monitoring study and appendices.
Stage one datasets
The historic datasets used for comparison for this monitoring programme are from the following studies:
- Healthy Routes: two rounds of data collection to support the development of Lambeth’s Healthy Routes
- 20mph Study: data collected by LB Lambeth to underpin analysis of the 20mph boroughwide speed limit
- The Floow: GPS telemetry data, providing detail on vehicle routing through neighbourhood cells; this data will be used indirectly to create a scaling factor to adjust Healthy Routes data for roads where no historic data was collected
Through the monitoring programme, a large amount of new data is being collected across the borough.
- We have generally used the same locations as those used in the Healthy Routes or 20mph studies to ensure a fair comparison, although some additional sites have been added, and these will need to make use of The Floow data instead.
- All new data has been collected via Automatic Traffic Counters (ATCs), which are installations that consist of two pneumatic tubes spanning the width of roads to be surveyed. These capture 15 vehicle classes based on number of vehicle axles and the distance between axles and are regularly used across the transport planning profession to capture traffic information.