News & Updates
DADSS Research Program | March 6, 2018
DADSS Research Program Technical Update
In late 2017, the DADSS Program made substantive progress towards its goal of producing a first-of-its-kind technology that would automatically detect when a driver is intoxicated. Over the last few months, the team has received and begun testing the latest prototypes, overcome some technical challenges, improved existing systems and discovered new information about the absorption of alcohol by the human body—all while preparing for the kick-off of field testing in 2018.
SenseAir Breath-Based Sensors
In late 2017, the DADSS program began working with the newly developed SenseAir Generation 3.1 Breath-Based sensors, for use in the Field Operational Trial (FOT) vehicles. The Gen 3.1 sensor has undergone rigorous verification and validation testing designed to simulate a sensor life of 15 years per the DADSS Performance Specifications. Testing was largely successful, but there are a few areas in which development is still needed for product certification. The sensors are currently being calibrated at various temperatures—including extreme cold and extreme heat—using dry and humidified sample reference materials that represent human breath at various alcohol concentrations. Using state-of-the-art Fourier Transform Infrared Spectroscopy instrumentation, these sample reference materials achieved precision targets that were four times better than the DADSS specifications.
The DADSS team successfully completed an external review of the development team’s technical approach and its method for technology validation. Additionally, the team pinpointed the cause of a previous concern surrounding the source of laser fluctuations in the Generation 4 sensor. The team was able to uncover the problem as an issue with the reference channel. Following this discovery, steps were taken to redesign the optical subsystems to correct the issue. A new optical touch pad system design and hardware update demonstrated improved optical performance in laboratory testing. The team designed and built a new electronic subsystem for the Generation 5 sensor and conducted preliminary testing and validation of the new STINGRAY laser package. Improvements were also made to the surrogate tissue samples for greater reliability and precision. The team also built and tested the first anti-circumvention prototype.
Human Subject Testing
We are also verifying and evaluating the sensors using human subjects in a controlled laboratory setting at McLean Hospital, a Harvard Medical School affiliate. To date, we’ve worked with 94 subjects, from whom, we’ve collected more than 5,500 blood samples. With this data, substantial progress has been made in measuring the alcohol absorption and elimination curves across various “drinking” scenarios. Results from this testing indicate that the scenarios have an effect on the alcohol pharmacokinetic curves. For example, exercise causes a rapid increase in the rate of absorption of alcohol, dispelling the myth that exercise can “burn off” alcohol. Also, how much you eat while drinking can affect the rate of absorption, with a full meal slowing the rate of alcohol absorption more than a snack. The “last call” drink consumed at the end of a drinking session not only causes alcohol measurements to spike, but increases the blood alcohol concentration and breath alcohol concentration even more than a similar drink consumed at the beginning. Across the range of scenarios, a solid linear relationship between blood, breath- and tissue-based alcohol readings has been established. This indicates that the measurements produced by the various generations of breath-based and touch-based prototypes is consistent, reproducible, and correlates very well with the gold-standard method of measuring alcohol in the body—blood via gas chromatography.
Pilot Field Operational Trials (PFOT)
The DADSS team completed the development of the PFOT Test Plan for the observation and use of the DADSS sensors in a real-world driving environment. This includes the identification of regional sites which explore varying environmental conditions as well as the development of operational and system requirements for day-to-day operations at each regional site. The team also completed the integration of four breath-based sensors into a platform Chevrolet Malibu that will be used to evaluate vehicle integration procedures and test the sensor and the data acquisition system performance. The PFOTs now await approval from the Office of Management and Budget.