Introduction
iNode's Junction Module is a core component of SMATS' analytics platform, purpose-built for monitoring and analyzing intersection performance in real time and over time. The module continuously processes GPS probe data to surface approach-level metrics, including control delay, travel time, turn ratios, and Level of Service, giving you the movement-level visibility needed to make evidence-based decisions about your intersections.
Before diving into your first study, it helps to understand the scope of analysis available so your boundary is drawn correctly and your results directly support the decisions you need to make. Rather than relying on point-based counters or manual counts, the Junction module builds a picture of intersection performance from actual vehicle trajectories, capturing how conditions vary by movement, time of day, and across different days of the week.
Each study covers a single junction. If you need to monitor multiple intersections, you will need to create a separate study for each one.
Metric and Use Cases
Metrics
The Junction Module delivers the following metrics:
- Delay and Stop Behaviour:
- Control Delay: The additional time vehicles experience at the intersection due to traffic control devices, including time lost in deceleration, stopping, queue move-up, and acceleration. A key factor in determining Level of Service (LOS).
- Approach Delay: Similar to Control Delay but measured on the approach only, excluding travel within or beyond the intersection.
- Queue Length: The estimated queue length in metres on each approach.
- Number of Stops: The number of times vehicles stopped on a given approach.
- First Stop Distance: The distance from the vehicle's first stop to the start of the junction, in metres.
- Speed and Travel Time:
- Travel Time: The total time a vehicle takes to traverse the approach from entry to exit.
- Average Speed: The average speed of vehicles on the approach.
- Deceleration Point Speed: The maximum speed of the vehicle within the approach road.
- Acceleration Endpoint Speed: The maximum speed of the vehicle within the exit road.
- Volume:
- Volume Per Hour: The estimated number of vehicles passing through an approach per hour.
- Turn Ratios: The percentage of vehicles from each approach exiting via each detected exit road.
- Level of Service:
- LOS Grade: A grade from A to F summarizing intersection performance based on control delay.
- AOG (%): Arrival on Green, the percentage of vehicles arriving during a green phase.
- Split Failure (%): The percentage of cycles where demand exceeds available capacity.
Use Case
The Junction Module equips transportation professionals, planners, and consultants with the ability to:
- Monitor and evaluate intersection performance: Track live delay, queue lengths, turn ratios, and Level of Service grades across movements and approaches to identify developing congestion, assess where intersections are operating efficiently, and flag signal timing issues as they occur.
- Support signal retiming and before-and-after studies: Use control delay and approach delay data to evaluate whether current signal timing is meeting performance targets, identify movements that would benefit from changes, and compare intersection performance before and after retiming, geometric changes, or policy interventions.
- Analyze turn movement patterns: Use turn ratios and volume data to understand how demand is distributed across movements at an intersection.
- Report on intersection performance: Communicate delay, LOS, and stop rates to stakeholders using consistent, probe-data-backed metrics.
It allows you to access defensible, continuous intersection performance data quickly, particularly where traditional data collection such as manual turning movement counts is not practical, budgets are limited, or ongoing monitoring is required.
Key Components and Workflows
The Junction Module makes it easier to analyze various metrics through a guided workflow, ensuring flexibility while keeping studies easy to set up:
- Junction Selection: Select the geographic boundary for your study, from specific segments to individual cities to entire regions.
- Result delivery: Access comprehensive result pages with clear summaries, visualizations, and data exports for deeper analysis.
Data Sources
At its core, iNode’s Junction Module is powered by high-resolution GPS probe data. Data is collected from:
- Connected GPS devices
- Embedded vehicle telematics systems
- GPS-enabled mobile phones
This data is continuously archived, creating a robust historical traffic database. The result is a rich, scalable foundation for travel time, speed and volume studies that combine real-time insights with long-term context, making the Route Monitoring module a key component of iNode - an advanced traffic data analytics platform.
Data Availability and Updates
Junction Module data is continuously updated as it moves through iNode’s processing pipeline, where it is cleaned, aggregated, and validated to ensure consistent, reliable results. Data is typically available with a one-day lag, meaning studies can be submitted for as recent as yesterday or today; however, to achieve optimal sample sizes and the highest data quality, we recommend waiting up to 72 hours before submitting a study, as some GPS data providers deliver data with delays beyond 24 hours.