- 这个毒品测试仪可以识别唾液中的安非他明、阿片剂、可卡因、大麻、美沙酮和其他管制毒品。(Dragerwerk AG)
Despite the introduction of active and passive safety systems installed on new vehicles, the U.S. motor vehicle death rate remains high, currently some 40,000 persons. Although this number includes 6,000 pedestrians (and not all deaths involved a crash), the total is alarming.
And significantly, 28% of all motor vehicle fatalities—over 10,000 persons—involve an alcohol-impaired driver, with a blood-alcohol content level (BAC) of at or over of 0.08, or 80 mg alcohol per deciliter of blood. (Utah is lowering its BAC limit to 0.05 this year). In accidents that result in a pedestrian fatality, 13% of the drivers and 33% of the pedestrians involved were alcohol-impaired.
Despite efforts by law enforcement to identify alcohol-impaired drivers, the problem remains. This has led to intensified work on development of in-car detection of high-BAC sensing equipment that can accurately detect a drunken driver and prevent him from starting and driving a car.
Infra-red technologies in testing
There are two infra-red technologies under current investigation by a research consortium, one system that is breath-based, another that is finger touch-based. The work, underway for nine years, is sponsored by NHTSA and the Automotive Coalition for Traffic Safety (ACTS), an organization of 16 vehicle OEMs. Also participating is a host of traffic safety NGOs. The project is called the Driver Alcohol Detection System for Safety, or DADSS.
The breath-based system is not like the breathalyzer used by police, which requires a deep-breath air sample for analysis. Rather, it takes a sample of the driver’s normal exhalation, which is primarily carbon dioxide. The sensor directs infra-red beams through it, and an electronic module analyzes the return waves. Because infra-red wavelengths vary according to the concentrations of different gasses through which they pass, the percentage of alcohol in the sample can be measured by the module.
This operating principle is somewhat akin to the operation of infra-red type automotive A/C refrigerant identifiers, and to some A/C refrigerant leak detectors.
The touch-based device, which likely would be built into an engine start button, illuminates and sends infra-red light through the skin into the capillaries of the fingertip. Like the breath-based system, infra-red beams are reflected back into the sensor. The touch-based system, using specific filters, looks for the two wavelengths that indicate the presence of alcohol—and only those wavelengths.
Both technologies have been developed to the points where they can take readings very quickly. The touch-type is being tuned to take several readings in under a second. The breath type is reportedly not nearly as fast, because of its type of operation (waiting for the driver to exhale), but the system response is instantaneous once the sample is taken.
Although the two systems are technically feasible, making them technologically usable requires continued research. The hardware must shrink in size, and the objective is to make it the size of a smartphone, while maintaining its fast action. However, its precision and reliability under all environmental conditions still must be proved. And of course, the technology must operate seamlessly, that is produce an engine-will-not-start signal with all-natural actions by the driver.
The systems also have to be reasonably resistant to defeat tactics. The program’s equipment quality level is set at Six Sigma (99.9997%) plus U.S. Department of Defense technology/manufacturing readiness levels.
The prototype testing for the breath-based system lends itself to a long-employed laboratory approach: use of a simulator, in this case for human breath. It produces an artificial equivalent to human breath, by combining carbon dioxide, plus some nitrogen and oxygen, and normal amounts of moisture. Ethanol is added in test concentrations for alcohol identification.
Airborne dust, and changes in temperatures and the simulation of a wide range of human movements all can additionally be incorporated.
Also in the research stage is location of the sensor, with the driver’s side door and steering column among the possibilities. In addition, the research teams are looking at the possible value or need to use more than one sensor, to identify locations that would positively separate the driver’s breath sample from those of passengers.
The system was developed by a pair of Swedish companies—the sensor by Senseair, working with an automotive safety supplier, Autoliv Development.
Touch-based detection research must take a totally different approach; a calibration device was developed that simulates characteristics of human tissues—because each person’s skin is of different thickness. In addition, of course, actual human testing has been underway. The system is being developed by TruTouch Technologies, a U.S. company that makes devices to detect alcohol impairment in workers arriving at a workplace. Its data shows a virtually exact match in accuracy compared with breath-based systems, although its work-entry devices are not designed to perform with the same speed as its automotive touch system.
Ensuring that a touch device is used by the driver alone will require a high level of verification that the actual driver is in the seat. It could be a combination of a facial-recognition sensor and a seated driver presence sensor. As currently configured, the system will not generate a valid engine-start signal if other than a seated driver presses the start button.
The system would be a vehicle option, and although vehicle installations and field testing is starting this year, the consortium has not gone beyond “a step closer” assessment of OE production. Although the BAC detection would be set at 0.08, a parent would be able to program the device to a no-start for drivers under 21, with an even lower BAC level if desired.
Instant reset is a feature of either system, so a designated driver could take over, or the motorist could take a nap and retest himself later.
Drug impairment needs attention
While safety agencies and law enforcement are working to enforce drunk driving laws, NHTSA also is looking at drug-impaired motorists. Although there is profuse data on alcohol impairment, there is little on the adverse effect of drug use. The data that is nationally cited is from the few states that have police officers trained to detect it, and simple Q&A surveys.
NHTSA data shows that use of marijuana, the most common drug, rose from 16.3% in 2007 to 20% in a 2013-14 survey of nighttime, weekend drivers. However, with marijuana legal in many jurisdictions, and no standards in force, even the availability of saliva/sweat testers are little more than sources of basic data. State laws on evidence of impaired driving, followed by police-performed visual tests (driver walking, etc.), are sometimes acceptable in court, but widely-accepted legal definition and real enforcement still are in their infancy.
Several drug testers are in use, both in states like Michigan which has legal restrictions on drugged driving, and Canada. The typical tester can perform an analysis in a couple of minutes, identifying most commonly used drugs.
Author: Paul Weissler
Source: SAE Automotive Engineering Magazine