SSI Zero-Speed Profiler Outperforms at ICART Rodeo
SSI Zero-Speed profilers confirm compliance according to AASHTO r56 standards
SSI participated in a Stop-and-Go (SAG) profiler rodeo with our Zero-Speed profiler in November 2024 at the ICART facility near O’Fallon, Illinois. The purpose of the study was to determine the current achievable accuracy and repeatability of SAG profilers. The data collections were designed to validate SAG profilers from all vendors. Preliminary results were presented at the RPUG conference in May 2025 (rpug.org).
*The final report of the November 2024 SAG rodeo has not been released. This article references the verbal presentation at RPUG and data that SSI has access to.
Background
This study will assist the revised publication of AASHTO r56 to include SAG certification. In 2025 there are two locations in the USA that are certifying SAG profilers using the AASHTO r56 thresholds for accuracy and repeatability; ICART and Caltrans. Caltrans test method 387 utilizes the same four speed profiles that were performed at the ICART rodeo. The current ICART method only includes one stop in the middle of the certification track. For more details on the speed profiles, reference CTM 387 which is already published and in use (https://dot.ca.gov/-/media/dot-media/programs/engineering/documents/californiatestmethods-ctm/ct-387-sep2023-a11y.pdf).
Participating Equipment
Each of the nine candidate profilers traveled to O’Fallon, Illinois from different profile vendors and state agencies. The group of profilers included non-SAG devices as a control group.
Data Collection
All profiling systems collected the ICART track under the four speed profiles for Stop-and-Go certification along with constant speed collections typically performed under AASHTO r56 certification. These collections are performed on the ICART certification loop, which has reference profiles for the accuracy comparison.
In a new development for the industry, the ICART track is now conducting high speed reference collections using their ULSP (Ultra Low-Speed Profiler). Having the ability to collect reference data multiple times each day assures the reported accuracy comparisons to the candidate profilers have minimal error. Furthermore, tests were conducted with RTK GPS corrections to determine a drift error. This testing explains how much accuracy results falter if operators drive 1-inch, 2-inches, or 3-inches off of the marked reference line.
Figure 4 & 5 from the Caltrans CTM 387 document, explaining the four speed profiles by time and speed.
Results and Analysis
Only two participating devices achieved the minimum accuracy (90%) and repeatability (92%) scores required to certify under AASHTO r56 for all four SAG speed profiles, per the 2025 RPUG presentation of preliminary results.
The SSI Zero-Speed profiler from Nevada DOT and the SSI vendor vehicle were the only compliant profilers. The minimum accuracy for the participating SSI systems was 92%, compliant with the 90% minimum for AASHTO r56 certification.
Once the full report is released by ICART and Applied Pavement Technology, it will be linked here.
