Seeing is believing: Visualising bus journey speeds

We regularly hear from our customers, colleagues and industry experts about the impact of delays to bus services, and the long-term damage they cause to the perception of bus reliability and convenience, and to the cost of operation. It has traditionally been very difficult to demonstrate the severity of delays on bus average speeds with many issues disregarded as anecdotal or lacking in evidence.

In 2023, Portsmouth City Council approached our Public Transport team at ITP to ask if there was a way to visualise post-Covid bus speeds in the city and use that information to develop solutions to get buses moving. The answer was yes, and by using our Public Transport Speed Visualisation tool this could be delivered quickly and cost-effectively.

The City

Portsmouth is the most densely populated city in the UK, with a road network that leaves little opportunity for dedicated bus priority. As part of their successful BSIP bid, Portsmouth City Council is investing over £48m to shorten bus travel times, improve reliability and satisfaction, and increase the number of bus journeys.

Portsmouth City Council works with local bus operators First and Stagecoach in an Enhanced Partnership. The partnership is hugely successful and has delivered improvements in ticketing, vehicles, marketing and service provision. As such, both operators were excited to be involved in the project and provided data for analysis.

The Challenge

To focus on improving the slowest journey speeds, the challenge was to use real-life bus data to build a tool to enable a greater understanding of conditions on the network, and to help focus BSIP funding where it is most needed.

Data Driven

So how do you turn huge volumes of ticket machine data in to a meaningful and accessible view of journey speeds? Giles Lipscombe, Principal Consultant at ITP, developed a solutioon to calculate bus speeds from GPS data by connecting data records to the road network. A similar approach was taken to one used for a project in Odesa, Ukraine, where we used technology to carry out a multi-modal, city-wide public transport speed analysis.

Although GPS appears to be extremely precise and consistent when used in smartphones or satnav systems, this is actually the result of sophisticated processing and correction algorithms. In its raw form GPS can be imperfect, particularly in urban areas where nearby buildings can affect the satellite’s signal and cause the indicated location to jump around, even when the vehicle is not moving. To get an accurate and realistic view of the speed, some mitigation measures need to be put in place. Our tool matches data to location, constraining the indicated location to the roadway and use these to calculate the movement of buses, using the simple assumption that buses don’t drive through people’s gardens!

Once the data has been cleansed and matched, the on-road distance between each GPS observation is used to calculate the speed, applying the observation to short links of between 100 – 200 metres of road segment. Thanks to the keen support of the bus operators in Portsmouth, we had over 4 million data points to analyse – almost all bus movements in November 2022 – giving us thousands of individual observation to work with on each link. This is a perfect sample size for calculating a reliable average but, better still, let us dive down to the day and even hour, while still having enough data to average away the outliers.

Finally, we analysed the data outputs and focused in on the lowest link speeds in Portsmouth. For ease, we applied patronage weightings to each service, using average loadings supplied by the operators to understand how many bus users were inconvenienced by the slow journey speed. However, the tool can also include real patronage data where available.

Putting Portsmouth on the Map

The outputs of the delay analysis are shown below. This heatmap shows journey speeds on weekdays between 16:00 and 17:59.

Targeting the slowest link speeds, a selection of bus priority concepts were developed for each link, or group of links. We tested these options with the project team, Portsmouth City Council’s highways team and the operators, refining the list with a focus on practical solutions that could be delivered within the BSIP funding timeframe.

Each option was appraised using the DfT Small Scheme Appraisal Toolkit to calculate the cost/benefit ratio and the outputs shared with Portsmouth City Council and the wider Enhanced Partnership.

The data and findings are now being used to inform and deliver schemes throughout the City. Paul Walker, National Bus Strategy Delivery Manager for Portsmouth City Council said, “The outputs from ITPs study are so insightful, and are really helping us focus on delivering the maximum improvements for bus users in the City.”

The tool brings a unique view of bus movements and constraints on the network. It can be used to visualise delays without the need for time consuming and expensive surveys and modelling, making it the ideal partner for BSIP projects throughout the country.

Where often the bus sits lower down the pecking order, this tool puts the bus first, bringing a unique view of actual bus movements and highlights where they become delayed on the network. It enables delays to be visualised without the need for time consuming and expensive surveys and modelling, provides officers with a practical solution, providing the information they need to make changes which will actually benefit the bus, making it an ideal solution to support BSIP projects throughout the country.

Emma Taylor, Associate Director, ITP
emma.taylor@itp.rhdhv.com