Project Owner

The San Diego Association of

Governments (SANDAG)

Prime Contractor

Parsons Corporation


20-mile stretch between San Diego and Escondido, California, USA


2011 – ongoing

Two-time Winner of the California Transportation Foundation Award for Operational Efficiency

San Diego Interstate 15 Integrated Corridor Management System




To provide a real-time modeling tool for the decision support system (DSS) as part of the pioneering integrated corridor management system (ICMS) on Interstate 15 (I-15) in San Diego.


SANDAG expects the ICMS project to help with the implementation of multimodal and smart growth principles, to improve safety throughout the corridor, increase traveler information mechanisms, institutional partnerships and networked transportation systems, both during recurrent and nonrecurrent conditions. The USDOT’s final objective is to roll out the ICMS nationwide, so that every large city can derive some benefit from what is being achieved in San Diego.

Aimsun Role

As part of the development and delivery of the I-15 ICM, Aimsun Live provides analytical and model-based predictions across the network, allowing traffic center operators to identify potential problems and congestion, and to evaluate multiple mitigation plans using real-time simulation. This has helped to reduce congestion associated with non-recurring events.


The I-15 Aimsun Live is based on a microsimulation model that accurately predictions in near real-time (under 5 minutes) for the next 60 minutes and provides typical transportation metrics in 15-minute time slices. These metrics include: flows; speeds; travel times; delay; queuing; volume/capacity ratios; turning counts and more.


These metrics apply, where appropriate, at various levels: network level; route level, section/link level, node level and turn level.


Aimsun Live runs 24/7/365, helping provide the metrics supporting the decisionmaking process and managing corridor assets such as VMS, Signals, and Ramp Meters.


The I-15 system and model required multiple rounds of stakeholder meetings including the main client (SANDAG), the stakeholder agencies (Caltrans, Cities of San Diego, Poway, and Escondido, and San Diego Metropolitan Transit System) and external vendors for signals, detection and other elements. It was critical to integrate the knowledge from each partner to ensure correct system understanding, implementation, and user training.

Data Management

Aimsun Live automatically collects real-time network status information 24/7 from multiple systems including different signal systems, detection sensors, real-time and planned events, mobile sources and ITS devices. This information is then combined within the simulation model to provide a current supply-and-demand view of the situation. The 60-minute simulation results are then displayed to provide better corridor monitoring. These predictions are also used to track impacts of the configuration of the network against typical conditions to alert operators to problems.


A key data input to Aimsun live is the detections traffic data (counts and speeds) that are aggregated and combined from multiple sources to create the appropriate view of the current Demand on the network. This demand is key to being able to accurately predict the next 60 minutes.


Through connections to all the external and internal data systems, Aimsun Live collects all event data, planned or unplanned, and applies the appropriate constraints associated with the events (lane closures, speed reductions, traffic actions…). Using data analytics and the outputs from the real-time predictions, the system has been able to identify and quantify the impact of events in terms of congestion and use that evaluation to determine the appropriate actions to manage the events if the impact is predicted to be server enough.


Aimsun Live disseminates all information to the central system (ICMS) that then handles the dissemination of relevant data to the customers and partner agencies.


The ICM system and Aimsun Live is a continually changing environment that must incorporate new systems and software packages; this has included changes to the external systems for the Signals and for the Ramps, and advances in the Aimsun modeling software package.


The system is monitored in real time and performance is reviewed monthly by the Project Development team (PDT). The PDT recommends updates to rules to capture any changes and updates the team on critical network changes that are incorporated into the models. Last year, as a result of these reviews, model accuracy and the scoring system were greatly enhanced. As signals are a critical component of the ICM network management, the model is configured to update the signal times every day to ensure proactive updates rather than waiting for a manual notification.


Part of the success of the ICM system is due to good management practices including an open channel of communication with the client and partners, automated alerts for systems failures or errors, and good documentation to help with training and knowledge transfer.


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Cite Aimsun Next

Aimsun Next 24

Aimsun (2024). Aimsun Next 24 User’s Manual, Aimsun Next Version 24.0.0, Barcelona, Spain. Accessed on: April. 16, 2024. [Online].


Aimsun Next 24

@manual {AimsunManual,
title = {Aimsun Next 24 User’s Manual},
author = {Aimsun},
edition = {Aimsun Next 24.0.0},
address = {Barcelona, Spain},
year = {2024. [Online]},
month = {Accessed on: Month, Day, Year},
url = {},

Aimsun Next 24

T1 – Aimsun Next 24 User’s Manual
A1 – Aimsun
ET – Aimsun Next Version 24.0.0
Y1 – 2024
Y2 – Accessed on: Month, Day, Year
CY – Barcelona, Spain
PB – Aimsun
UR – [In software]. Available: