RTC is the public transit agency for Quebec City, Canada. It ensures the mobility of people in the urban agglomeration of Quebec City by offering public transport and promoting the integration of different travel solutions.
Bus bunching is a problem faced by transport authorities around the world and for RTC there is no exception. The organization is responsible for more than 4000 trips by over 600 vehicles each day. High-frequency routes account for 60% of rides and present a big challenge for planners trying to ensure equal spacing and maintain service quality.
In search of a data-driven solution to bus bunching, RTC turned to SimWell - an industrial engineering company supporting business decisions with simulation, data science, and optimization, based in US and Canada. SimWell’s solution to the bus bunching problem involved simulation modeling with AnyLogic.
RTC had a global vision for their project with detailed specifications, and quality first approach that centered on stakeholder involvement. This project was built on three main guiding principles:
- Building on what had already been achieved (the simulation model would become a component of a bigger project, built around six sigma concepts and help test ideas coming from other activities);
- Autonomy and flexibility (model could be a standalone application with easily changable parameters);
- Change management (the entire project, including the model, was built with change management and stakeholders in mind).
In a perfect world, every bus would arrive at a stop according to plan to most efficiently serve customers. In reality, several problems can occur: traffic congestion, schedule gaps and coincidences, overcrowding and uneven loads, etc. All of these create problems for customers and impact on the rest of the transit line.
The objective of this project was to improve service quality for the customers while maintaining or improving the quality of work for bus drivers. Using a simulation model, engineers wanted to test solutions and see their potential impact and risk for customers and bus drivers before deployment into the real world.
One of the main goals of using the simulation model for transportation system analysis was to figure out the best solution to solve the bus bunching problem. Another goal was to allow stakeholders and decision-makers to witness experimentation and see how solutions physically operate and not just with tables and statistics. AnyLogic’s UI and 2D and 3D animation capabilities fully covered these requirements, providing multiple views and strong features.
Implementation flexibility thanks to JAVA extensibility and the ability to package the model as the standalone application was also a big advantage of using AnyLogic as transportation modelling software. The solution allowed the model to run without being installed on end user’s machines.
The Solution Infrastructure
The model focuses on short-term corrective actions. The long-term decisions are modeled by changing the input data.
The historical data for the model was taken from bus information systems:
- GPS locations
- Automatic passengers counter (APC)
- Travel time
- Driver break time
The information helps reproduce the trip processes and bus capabilities. Different sorts of variability are also captured in the historical data, such as traffic congestion, traffic lights, seasonal factors, overcrowding, etc.
The model is fed historical data extracted from RTC data warehouse. It allows calibration of different functions of the model, such as travel times, driver behaviors, ridership at the various stops, etc. Then, to test bus frequencies and schedule runtimes, schedules are taken from the RTC planning software.
The simulation model provides matrix visualization and information for that can be used in decision making. The model supports various kinds of operation simulations: adjust the schedule, build preventive or corrective action policies for the control center, give the board a decision brief about strategic or technical decisions, such as such as determining service levels, changing operating modes, or any other important changes to the process.
For the reference scenario, engineers used the data from 2018 and 2019 – before the pandemic, to give a baseline. The team included various data for analysis:
- Bus time at each stop (open doors duration, alighting and boarding time, additional constant time (e.g. fare), traffic lights).
- Passenger arrival rate at a bus stop.
- Passenger destination probability (how many people board and alight on the different stops on the line).
- Running time (based on the Markov chains principle, the time for each next pair of stops depends on the previous one).
Key Performance Indicators
There were no existing KPI that represent what customers and bus drivers experience in a high frequency environment. Now, with simulation modeling, it is possible to calculate several indicators and compare them to real life data:
- Irregularity measure, represents the variation from the planned headway (%);
- Excess wait time (EWT), represents the additional time customers had to wait (min/passanger);
- Passengers comfort levels, can only be calculated in a simulation environment.
The simulation model, created by SimWell for RTC, allows experimentation based on input data, and the assessment of multiple ideas and combinations in the search for better solutions to bus bunching.
Engineers are currently planning the next phases and may include a gaming module for training operation controllers. Another possibility is the addition of transportation optimization of the next days’ frequencies and schedules, based on resource availability and runtime predictions.
Additionally, there is the possibility to create a digital twin that could be used to trigger action suggestions for drivers for preventive or correcting action.
The case study was presented by Pierre-Olivier Bédard and Nomessi Kokutse, of RTC, and Denis Matarangas, of SimWell, at the AnyLogic Conference 2021.
The slides are available as a PDF >>