Acquire microsimulation model calibration & validation data using 1-hertz TLAP

Introduction: While this tool will not be the best choice for many situations, when conditions require what 1-second TLAP does best, it is highly cost-effective and it will enable your team to create and calibrate complex microsimulation models that might not otherwise be successfully completed. If you call Skycomp and describe your potential application, we can tell you about the strengths and weaknesses of all of your options, and we will refer you to an appropriate expert if an alternative method will provide you with better or more cost-effective results.

Discussion: Before investments can be made to improve mobility and eliminate bottlenecks, a process must be followed involving engineering analysis, stakeholder consensus building, and staged approvals. A well-built microsimulation model can be invaluable for all steps of this process. However, creating models of networks where travel patterns are complex pose two special challenges: first, how do you measure the complicated traffic flows that your model must replicate accurately? And second, if you have done that successfully and built a quality model, how do you establish its credibility with the audiences it was intended to enlighten (particularly when there are groups determined to fight anything you do)?

In theory, this is what surveillance drones could help us with in the future, after the legal and liability issues have been resolved that today preclude the use of high-altitude drones above populated areas. Cameras could record the movement of all vehicles, allowing the tracing of routes and true O-D patterns, or showing changing levels of congestion severity, or even parking occupancy and turnover rates, travel times, speeds & delays on any route, traffic signal operations, or simply enabling the counting of volumes or turning movement counts anywhere that is visible. The resulting variety of metrics and the granularity could not be matched by any other technology, at any cost. Next, aerial imagery could be juxtaposed with model calibrations to emphatically show that the model replicates reality. Lastly, additional metrics could be taken from the imagery later if additional needs are thought of.

Inspired by this vision and pressed by clients, Skycomp began in 2012 to develop the capability to provide exactly these services, but fully sanctioned by the FAA. Renting local, unmodified helicopters near each survey site was the only way to keep it affordable, which meant that a walk-up mounting system had to be invented for the camera clusters. Other computer-assisted processes then had to be assembled to align all imagery and then extract the many types of traffic flow metrics. Success followed such that today Skycomp deploys helicopters that hold fixed-position hovers one mile high, and are able to image all specified highway links in two-hour continuous sets, at one frame-per-second (1-hertz or 3,600 high-resolution digital images per camera per hour).

Through 2016, Skycomp has successfully conducted 80 TLAP surveys of this type, in 17 states. These have involved deploying from one to four helicopters running from one to 16 cameras simultaneously, recording traffic flows on up to 16 linear miles of highway. All of these surveys have enabled clients to receive TMC’s, volume counts, O-D patterns, travel times and/or other metrics, “pre-balanced” because they were all acquired simultaneously, to build complex models with ease and confidence that could not have been achieved with any other tool. (Interestingly, Skycomp has frequently been asked to go back into the imagery later to examine areas and extract metrics that were not previously thought of.) Furthermore, different metrics acquired from the TLAP imagery can often be used for the very different tasks of first calibrating the model (e.g. using ramp volumes, TMC’s and/or O-D patterns), and then validating it with different metrics (e.g. queue development & queue lengths, and/or travel times).


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