A group of researchers from Northeastern University and the University of Arkansas issued a report this February “Did Electronic Logging Device Mandate Reduce Accidents?” which analyses the effects of the electronic logging device mandate, and they reached two main conclusions:
- The use of ELDs has not reduced the rate of truck crashes
- The frequency of speeding violations, particularly among the small carrier segment, has increased since the mandate took effect
The report mostly focuses on smaller carriers and owner-operators who were considered the most impacted by the mandate, since larger carriers were likely already using ELDs or AOBRDs.
Although there were fewer hours of service violations, crash numbers saw little impact by the enforcement of the ELD mandate.
The report studied drivers between January 1, 2017 and September 1, 2018, which included:
- Nearly a year’s worth of data prior to the December 18, 2017, enforcement deadline of the ELD mandate, and
- Roughly three-month light enforcement period ahead of the April 1, 2018, hard enforcement date
For the pre-enforcement period, researchers said there was an average of 1,717 truck crashes a week. That number spiked during the soft enforcement period (December 17, 2017, to April 1, 2018) to 1,912 crashes a week. After April 1, the number dropped to an average of 1,703 crashes per week.
- Independent owner-operators averaged 154 crashes a week prior to the ELD mandate December 2017 deadline and 160 crashes after hard enforcement began in April 2018.
- Drivers at carriers with between 101 and 1,000 truck averaged 374 crashes a week before the mandate and 361 crashes a week after hard enforcement began.
- Carriers with 1,001 or more trucks saw their crash rates dip slightly, from 244 a week to 240 a week.
Based on this data, the researchers conclude that these numbers do not point to any obvious reduction in accidents due to the ELD mandate.
While accident rates appear unchanged, the report says, unsafe driving behaviors such as speeding appear to have increased over the same period of time. These unsafe driving behaviors were found to be in response to productivity losses caused by the mandate.
According to the report, unsafe driving violations:
- By owner-operators increased by as much as 33.3%, and speeding increased by as much as 31%
- Carriers with between 101 and 1,000 trucks saw only a 6% increase in the number of unsafe driving violations per week after hard enforcement of the mandate began
- Carriers with more than 1,000 trucks saw a 12% increase in unsafe driving violations after ELD enforcement began
“We find that the ELD mandate unequivocally enhanced HOS compliance,” the researchers write. “However, the ELD mandate did not noticeably improve safety, and we are able to produce no statistically significant evidence that ELD adoption by the smaller firms corresponded to any reduction in accident rates.”
The Biden Administration and a Democrat-controlled Congress have the opportunity to reshape trucking regulations this year. Looking at what the Obama and Trump administrations left unfinished can show a potential roadmap to changes on the horizon.
Josh Fisher
From driver classification laws to hours of service changes to safety technologies and insurance minimums, the Biden administration and Democrat-controlled Congress have the potential to reshape trucking regulations over the next few years.
With the slimmest majority possible in the U.S. Senate and just a 10-vote advantage in the House, there could be pressure on the Democrats to push through new regulations and revisit Obama-era changes that the Trump Administration put off or canceled. The Biden Administration has already put a hold on some late-2020 trucking proposals’ by Trump’s DOT — including a pilot program to look at allowing drivers to pause their on-duty driving period.
Other Democrat-led ideas, such as increasing the minimum insurance for trucking companies, could get rolled into an infrastructure bill that Democrats expect to push for this spring.
Based on interviews with industry experts and past coverage of the FMCSA and DOT, FleetOwner has highlighted 10 pending or potential changes to the trucking industry worth keeping an eye on in 2021.
Driver classification laws: On hold
The Trump administration’s Department of Labor-proposed rule that aimed to clarify the difference between an employee and an independent contractor under the Fair Labor Standards Act has been put on hold by the Biden administration. Democrats have argued that this law would make it easier for employers to classify workers, such as truck drivers, as contractors to avoid paying benefits and employment taxes.
Insurance liability increase: Likely
The minimum insurance requirement for heavy-duty vehicles hauling non-hazardous freight stands at $750,000. In 2020, the U.S. House’s $494 billion highway bill included an amendment that would increase the insurance minimum to $2 million. With Democrats in control of Congress and the White House, expect this proposal to be part of any future infrastructure bill and $2 million could be the floor — not the ceiling — of proposed requirements.
Speed limiters: Likely
The Trump administration shelved the Obama administration’s proposal to require speed limiters on large trucks. Democrats pushed for this to be part of the 2020 infrastructure bill that passed the House. This is expected to be part of the 2021 proposal or return as a proposed rule from Biden’s DOT.
Automatic emergency braking: Likely
During the Obama administration, passenger vehicle manufacturers agreed to include automatic emergency braking (AEB) on all new cars and light trucks by 2022. AEB could be mandated for new medium- and heavy-duty trucks as part of an infrastructure bill out of Congress or by the DOT.
Sleep apnea screening: Likely
Another Obama-era rule proposal eschewed by Trump’s DOT would require obese drivers to be screened for sleep apnea, which some studies have shown affect about a third of commercial drivers. In the old proposal, drivers with a body mass index of 40 or higher would be flagged for screening and others with a BMI of 33 or higher could be subject to screening if they meet other criteria. Expect this to be a Biden-era priority.
Trailer underride side guards: Possible
Expect the new DOT to take a serious look at strengthening rear-underride guards for trailers and considering adding a requirement for guards on the sides of trailers. The trucking industry and safety advocacy groups have been at odds over underride guards for years. Bipartisan legislation to add the requirements was last proposed in 2019 and saw pushback from trucking groups that said it would cost the industry billions of dollars. This could be part of an infrastructure bill or the Federal Motor Carrier Safety Administration (FMCSA) could propose a rule.
2020 HOS changes: Here to stay, but…
The new hours of service (HOS) rules that went into effect in September 2020 are likely to stick around in some form. The significant HOS changes expanded the short-haul exception to 150 air miles and a 14-hour work shift; expanded the adverse driving conditions exception by up to two hours; redefined the 30-minute break requirement; and modified the sleeper berth exception to allow a driver to combine at least seven hours in the sleeper with off-duty time. In December, Congress directed FMCSA to analyze how the new rules impact highway safety compared to the old rules. Scopelitis Transportation Consulting (STC) anticipates the Biden Administration to want even more analysis. David J. Osiecki, president of STC, told FleetOwner that he doesn’t expect rolling back the 2020 rules to be high on the new DOT’s priority list.
Pause the HOS clock pilot: On hold
A proposal that didn’t make it into last year’s new HOS rules, which would allow drivers to pause their on-duty driving period with one off-duty period up to three hours, was introduced late in the summer. FMCSA proposed a pilot program to study the proposal. That is among the midnight regulations put on hold by the new administration.
Under-21 interstate drivers pilot: On hold
The American Trucking Associations-backed pilot program to evaluate allowing commercial drivers younger than 21 years old to operate CMVs in interstate commerce is back under review since Biden was sworn in. Younger commercial drivers are currently allowed to work in intrastate operations. It now appears their opportunity to join the interstate commerce workforce will have to wait as the pilot program is reviewed.
CSA: Expect refinement
The Trump administration tried to put its stamp on the Compliance, Safety, Accountability (CSA) scoring system but did not get a rule published in time. FMCSA worked with the National Academy of Sciences to look at some statistical challenges within that system and recommended the Item Response Theory in 2017 as an alternative to the CSA Safety Measurement System scoring method. Expect the new DOT to continue to look at refining CSA, which has now entered its second decade — and third presidential administration. Changes could come in an infrastructure bill, or FMCSA could look at other ways to refine the program.
Dr. Marc Green, PhD
This article should not be interpreted to mean that human perception-reaction time is 1.5 seconds. There is no such thing as the human perception-reaction time. Time to respond varies greatly across different tasks and even within the same task under different conditions. It can range from .15 second to many seconds. It is also highly variable. In many cases, the very concept of perception-reaction time simply doesn’t apply2.
1. A “standard” or “generally accepted” PRT cannot and does not exist;
2. Exact PRT values are almost always impossible to determine due to lack of data, to the impossibility of knowing when to start timing and to the general difficulty of going from the simplified research world to the real-world;
3. A PRT cannot be determined by cookbook methods such as “Olson”, AASHTO or a computer program;
4. Specifying PRT without specifying deceleration holds little value, since stopping depends on both. Drivers often trade them off. Braking at maximum possible deceleration cannot be assumed; and
5. PRT generally does not explain why a collision occurred. It is not a cause, but rather a symptom to be explained. The real cause lies in the answer to the question, “Why was the PRT insufficient?” By example, imagine that your car stops. Why? The gas gauge points to empty. Is that why the car stopped? No. Your car does not stop because the gas gauge needle points to empty. The guage is only an overt symptom and indicator, of being out of gas. The car stopped because it was out of gas, not because the gas gauge’s needle position. PRT is like the gas gauge. The empty tank is like low visibility, misplaced action boundary, response conflict, violated expectation, driver impairment, etc.
In many cases, the speed with which a person can respond, “reaction time,” is the key to assigning liability. It is common practice for accident reconstructionists simply to use a standard reaction time number, such as 1.5 seconds, when analyzing a case. In fact, reaction time is a complicated behavior and is affected by a large number of variables. There can be no single number that applies universally.
Reaction time is a surprisingly complex topic. Unfortunately, most “experts” used canned numbers without a good appreciation for where the numbers originate, how they were obtained or the variables that affect them. Moreover, there are several distinct classes of reaction time, each with somewhat different properties. In this article, I briefly describe some keys issues. The discussion focuses primarily on driver reaction time.
Reaction Time Components
When a person responds to something s/he hears, sees or feels, the total reaction time can be decomposed into a sequence of components.
1 Mental Processing Time
This is the time it takes for the responder to perceive that a signal has occurred and to decide upon a response. For example, it is the time required for a driver to detect that a pedestrian is walking across the roadway directly ahead and to decide that the brakes should be applied. Mental processing time is itself a composite of four substages:
- Sensation: the time it takes to detect the sensory input from an object. (“There is a shape in the road.”) All things being equal, reaction time decreases with greater signal intensity (brightness, contrast, size, loudness, etc.), foveal viewing, and better visibility conditions. Best reaction times are also faster for auditory signals than for visual ones. This stage likely does not result in conscious awareness.
- Perception/recognition: the time needed to recognize the meaning of the sensation. (“The shape is a person.”) This requires the application of information from memory to interpret the sensory input. In some cases, “automatic response,” this stage is very fast. In others, “controlled response,” it may take considerable time. In general, novel input slows response, as does low signal probability, uncertainty (signal location, time or form), and surprise.
- Situational awareness: the time needed to recognize and interpret the scene, extract its meaning and possibly extrapolate into the future. For example, once a driver recognizes a pedestrian in the road, and combines that percept with knowledge of his own speed and distance, then he realizes what is happening and what will happen next – the car is heading toward the pedestrian and will possibly result in a collision unless action is taken. As with perception/recognition, novelty slows this mental processing stage. Selection of the wrong memory schema may result in misinterpretation.
- Response selection and programming: the time necessary to decide which if any response to make and to mentally program the movement. (“I should steer left instead of braking.”) Response selection slows under choice reaction time when there are multiple possible signals. Conversely, practice decreases the required time. Lastly, electrophysiological studies show that most people exhibit preparatory muscle potentials prior to the actual movement. In other words, the decision to respond occurs appreciably faster than any recordable response can be observed or measured.
These four stages are usually lumped together as “perception time,” a misnomer since response selection and some aspects of situational awareness are decision, not perception.
2. Movement Time
Once a response is selected, the responder must perform the required muscle movement. For example, it takes time to lift the foot off the accelerator pedal, move it laterally to the brake and then to depress the pedal.
Several factors affect movement times. In general, more complex movements require longer movement times while practice lowers movement times. Finally the Yerkes-Dodson Law says that high emotional arousal, which may be created by an emergency, speeds gross motor movements but impairs fine detailed movements.
3 Device Response Time
Mechanical devices take time to engage, even after the responder has acted. For example, a driver stepping on the brake pedal does not stop the car immediately. Instead, the stopping is a function of physical forces, gravity and friction.
Here’s a simple example. Suppose a person is driving a car at 55 mph (80.67 feet/sec) during the day on a dry, level road. He sees a pedestrian and applies the brakes. What is the shortest stopping distance that can reasonably be expected? Total stopping distance consists of three components:
- Reaction Distance. First. Suppose the reaction time is 1.5 seconds. This means that the car will travel 1.5 x80.67 or 120.9 feet before the brakes are even applied.
- Brake Engagement Distance. Most reaction time studies consider the response completed at the moment the foot touches the brake pedal. However, brakes do not engage instantaneously. There is an additional time required for the pedal to depress and for the brakes to engage. This is variable and difficult to summarize in a single number because it depends on urgency and braking style. In an emergency, a reasonable estimate is .3 second, adding another 24.2 feet3.
- Physical Force Distance. Once the brakes engage, the stopping distance is determined by physical forces (D=S²/(30*f) where S is mph) as 134.4 feet.
Total Stopping Distance = 120.9 ft + 24.2 ft + 134.4 ft = 279.5 ft
Almost half the distance is created by driver reaction time. This is one reason that it is vital to have a good estimate of speed of human response. Below, I give some values which I have derived from my own experience and from an extensive review of research results.
Response speed depends on several factors so there can be no single, universal reaction time value. Here is a list of factors which affect reaction time. In all cases, the times assume daylight and good visibility conditions.
Expectation
Reaction times are greatly affected by whether the driver is alert to the need to brake. I’ve found it useful to divide alertness into three classes:
- Expected: the driver is alert and aware of the good possibility that braking will be necessary. This is the absolute best reaction time possible. The best estimate is 0.7 second. Of this, 0.5 is perception and 0.2 is movement, the time required to release the accelerator and to depress the brake pedal.
- Unexpected: the driver detects a common road signal such as a brake from the car ahead or from a traffic signal. Reaction time is somewhat slower, about 1.25 seconds. This is due to the increase in perception time to over a second with movement time still about 0.2 second.
- Surprise: the drive encounters a very unusual circumstance, such as a pedestrian or another car crossing the road in the near distance. There is extra time needed to interpret the event and to decide upon response. Reaction time depends to some extent on the distance to the obstacle and whether it is approaching from the side and is first seen in peripheral vision. The best estimate is 1.5 seconds for side incursions and perhaps a few tenths of a second faster for straight-ahead obstacles. Perception time is 1.2 seconds while movement time lengthens to 0.3 second.
The increased reaction time is due to several factors, including the need to interpret the novel situation and possibly to decide whether there is time to brake or whether steering is a better response. Moreover, drivers encountering another vehicle or pedestrian that violates traffic regulations tend to hesitate, expecting the vehicle/pedestrian to eventually halt. Lastly, there can be response conflict that lengthens reaction time. For example, if a driver’s only possible response requires steering into an oncoming traffic lane (to the left) there may be a hesitation.
Urgency
People brake faster when there is great urgency, when the time to collision is briefer. The driver is travelling faster and/or the obstacle is near when first seen. While brake times generally fall with greater urgency, there are circumstances where reaction time becomes very long when time-to-collision is very short. The most common situation is that the driver has the option of steering into the oncoming lane into order to avoid the obstacle. The driver then must consider alternative responses, braking vs. steering, weigh the dangers of each response, check the left lane for traffic, etc.
Cognitive Load
When other driving or nondriving matters consume the driver’s attention, then brake time becomes longer. For example, on a winding road, the driver must attend more to steering the car through the turns. Another major load on attention is the use of in-car displays and cell phones. There is no doubt that both cause delays in reaction times, with estimates ranging from 0.3 to as high a second or more, depending on the circumstances.
Stimulus-Response Compatibility
Humans have some highly built-in connections between percepts and responses. Pairings with high “stimulus-response compatibility” tend to be made very fast, with little need for thinking and with low error. Low stimulus-response incompatibility usually means slow response and high likelihood of error.
One source of many accidents is the human tendency to respond in the direction away from a negative stimulus, such as an obstacle on a collision course. If a driver sees a car approach from the right, for example, the overwhelming tendency will be to steer left, often resulting in the driver steering right into the path of the oncoming vehicle. The stimulus-response capability overrides and the driver simply cannot take the time to observe the oncoming car’s trajectory and to mentally calculate itsimple, reflexive uture position. In short, the driver must respond to where the car is now, not where it will be at some point in the future.
Most people have experienced this phenomenon when going into a skid. The correct response is to turn the wheel in the direction of the skid, but it takes practice and mental concentration to avoid turning the wheel away from the skid, which is the high compatibility response.
Psychological Refractory Period
Following a response, people exhibit a “psychological refractory period.” During this period, new responses are made more slowly than if there had been no previous behavior. For example, suppose a driver suddenly steers left and then right. The steer-right response will occur more slowly because it immediately followed the steer-left.
Age
Although most basic research finds that older people respond slower than younger ones, the data on older drivers’ braking times are not entirely clear. One problem is that different studies have used different definitions of older; that is, sometimes “older means 50, sometimes it could mean 70. Moreover, some studies find no slowing of reaction time with age. Instead, they conclude that the older driver’s greater experience and tendency to drive slower compensate all or in part for the decline in motor skills. [Note Added. Aging effects in PRT depend heavily on the task. For simple,reflexive responses, healthy older people show little slowing. For complex and/or low visibility tasks, however, they can be much slower.]
Gender
Although the data are not clear, it seems likely that females respond slightly slower than males.
Nature of the Signal
In the examples cited above, the driver detected a distinct signal such as a brake light, the appearance of a clear obstacle in the path, etc. Some braking cues are subtler and more difficult to detect, causing slower braking times.
One of the most difficult situations occurs when a driver must detect motion of the car immediately ahead, its acceleration or deceleration. Accidents frequently occur because the driver fails to notice that the car ahead has stopped and does not apply brakes until it is too late.
The general problem involves estimating time-to-collision (TTC. It is a tough problem for several reasons. One is that it is much more difficult to judge motion toward or away from you than it is to judge motion of something which cuts across your path. It’s simply a matter of optics. Humans, in part, sense motion by registering the movement of an object image projected on the retina, the light-sensing portion of the eye. The movement of the object’s image is much smaller with motion toward/away than with motion cutting across the frontal plane.
Second, it is more difficult to judge motion of the object ahead if we are moving as well. The visual system must then disentangle the retinal image motion caused by the movement of the object ahead from the retinal image motion caused by our own “egomotion.” This is far more complex a problem than judging motion of an object when we are stationary.
Third, the normal expectation is that cars do not stop in the middle of the road. Reaction time, as explained above, is much slower when people encounter a low probability or unexpected event.
Visibility
Reaction time increases in poor visibility. Low contrast, peripheral viewing, bad weather, etc. slow response. Moreover, virtually all reaction time studies have been performed in high light, photopic visibility conditions. At night in urban areas, vision operates in the mesopic range, so there is mixed rod-cone activation. The few existing data suggest that reaction time sharply increases as the rods become the primary photoreceptor.
On the other hand, there are some situations in which response is faster in low light. For example, light emitting sources, such as rail-highway crossing signals or brake lights, produce better reaction times at night. With no sun or skylight to reflect off the fixture and with a darker background, the signal has higher contrast and greater visibility.
Response Complexity
More complex muscular responses take longer. For example, braking requires lifting the foot from the accelerator, moving laterally to the brake pedal and then depressing. This is far more complex than turning the steering wheel. While there have been relatively few studies of steering reaction time, they find steering to be 0.15 to 0.3 second faster. Perception times are presumably the same, but assuming the hands are on the steering wheel, the movement required to turn a wheel is performed much faster than that required to move the foot from accelerator to brake pedal.
Reaction Time At Night
The same factors affecting reaction in daylight conditions operate at night. Light level per se, has little effect on reaction time. For example, one study found that under scotopic vision, decreasing light levels by a factor of ten only slowed reaction time by 20-25 msec (1/40 to 1/50 second.)
However, there are new variables at work. For example, a light which might have low contrast and low conspicuity during the day because the background is bright could become highly conspicuous at night and produce faster reaction times. Always remember that contrast is what matters: people see contrast, not light.
Complex Reaction Times
In his classic “On The Speed Of Mental Processes,” Donders (1868) proposed a classification scheme that experts still use to distinguish among three different types of reaction time, simple (Type A) and more complex situations, choice (Type B) and recognition (Type C). While most of the variables affect simple and complex types in the same way, choice and recognition reaction times each add new factors that must also be considered.
Choice reaction time (Type B) occurs when there are multiple possible signals, each requiring a different response. The responder must choose which signal was present, and then make the response appropriate for that light. This requires two processes not present in simple reaction time: 1) signal discrimination – decide which signal occurred and 2) response selection – choose the response based on which signal occurred. In the classic laboratory procedure, a person sits with his/her fingers on 2 different telegraph keys and waits for one of 2 different lights to flash. When a signal occurs, s/he releases the telegraph key assigned to that signal. Reaction time is again the time between light onset (signal) and release of the key (response.)
With multiple signals, the responder cannot simply detect the signal but must also recognize which signal occurred and then mentally program the correct response. These extra mental operations slow reaction. Choice reaction times slow as the number of possible signals increases according to the equation,
RT = a + b log2N
where a and b are constants and N is the number of alternatives. The equation has two terms. The “a” constant is simply the “irreducible minimum” reaction time in the situation. (The variable part is called “the reducible margin.”) The relationship between RT and the number of alternatives is nonlinear – doubling the number of alternatives does not increase RT by a factor of 2 but rather by the log of the number of possible signals.
In Type C, or “recognition,” reaction time, there are multiple possible signals but only one response. In this case, the responder makes the response when one stimulus occurs but withholds response when the other(s) appears. The standard lab version of this paradigm has a subject with his/her fingers on 1 telegraph key and waits for one of x different lights to flash. When the signal light occurs, s/he releases the telegraph. If one of the nonsignal lights occurs, then the subject should make no response. This is sometimes called the “go, no-go” paradigm. Reaction times are invariably longer than for simple reaction time. A good example would occur when a police officer confronts a “suspect.” The officer sees something in the suspect’s hand and must make a go (shoot) or no-go (don’t shoot) decision.
Final Comments
This article has focused on driver reaction times. While the basic principles generalize to estimating other reaction times, the exact numbers do not. Each type of reaction time has its own peculiarities that must be examined. For example, reaction time for a shooter who is tracking a target might be 0.3 second. but even this would be a function of trigger pull weight.
1This is a brief summary/elaboration of the article, “‘How Long Does It Take To Stop?’ Methodological Analysis of Driver Perception-Brake Times” Transportation Human Factors, 2, pp 195-216, 2000.
2See Green, M. (2017). Roadway Human Factors: From Science To Application. Tucson: Lawyers & Judges Publishig.
3I have made some simplifications here. First, some braking occurs during during the brake engagement period. This is best calculated by assuming that braking is half the maximum during the period. Recent data, however, suggests that the period is longer than than the 0.3 second described. Second, drivers do not always depress the brake pedal to maximum or brake in a single continuous movement, so full brake engagement may never occur. Third, vehicles with air brakes require an additional component, “brake lag”. Depending on the setting, air brakes have a .03 to .08 second lag before they engage. Most calculations use a nominal lag value of 0.5 seconds, adding another 40 feet to stopping distance.
