Distraction and impairment

Distraction and impairment both reduce a driver's ability to perceive hazards and respond in time. Distraction takes attention away from driving for a moment; impairment from alcohol, cannabis, other drugs or some medications degrades the brain's ability to drive for hours. Both are common, both are deadly, and both are among the leading contributors to serious collisions. This lesson explains how each affects driving, what the law says, and what drivers and employers can do. Fatigue, which impairs drivers in similar ways, is covered in lesson 6.

Three kinds of distraction

Distraction is anything that takes a driver's attention away from driving. It is often grouped into three kinds. Visual distraction takes your eyes off the road. Manual distraction takes your hands off the wheel. Cognitive distraction takes your mind off driving. Texting is so dangerous because it combines all three. But cognitive distraction alone is enough to cause collisions: drivers deep in a phone conversation, even hands-free, have been shown in many studies to miss more hazards and react more slowly than undistracted drivers, because the brain cannot fully attend to both tasks.

# Distance travelled "blind" while looking away (illustrative glance times).
for kmh in (50, 80, 100):
    v = kmh / 3.6
    for glance in (2, 5):
        d = v * glance
        print(f"{kmh:>3} km/h, {glance} s glance: {d:5.0f} m ({d * 3.281:5.0f} ft) travelled without looking")

 50 km/h, 2 s glance:    28 m (   91 ft) travelled without looking
 50 km/h, 5 s glance:    69 m (  228 ft) travelled without looking
 80 km/h, 2 s glance:    44 m (  146 ft) travelled without looking
 80 km/h, 5 s glance:   111 m (  365 ft) travelled without looking
100 km/h, 2 s glance:    56 m (  182 ft) travelled without looking
100 km/h, 5 s glance:   139 m (  456 ft) travelled without looking

Reading a short text message commonly takes around five seconds. At highway speed, that is more than the length of a football field travelled with eyes off the road. Research from naturalistic driving studies, in which cars were fitted with cameras and sensors for months, found that glances away from the road longer than about two seconds sharply increased crash and near-crash risk.

In-vehicle technology

Modern vehicles are full of screens: navigation, infotainment, fleet dispatch tablets and electronic logging devices. Many of these are useful, but every interaction takes attention. Good fleet practice is to set up navigation before departing, use voice prompts rather than looking at the screen, lock out or restrict dispatch tablets while the vehicle moves, and pull over safely to read job details or respond to messages. Advanced driver assistance systems, such as lane-keeping and adaptive cruise control, can reduce workload but can also tempt drivers to pay less attention. They are assistance, not automation, and the driver remains fully responsible.

The law on handheld devices

Every province and territory restricts the use of handheld electronic devices while driving. In general, drivers may not hold, use or view a handheld phone or other device while driving, including while stopped in traffic or at a light. Hands-free use through a mounted device or voice command is generally allowed for fully licensed drivers, but often banned for novice drivers. Penalties are significant and rising. In Ontario, for example, a first conviction for distracted driving carries a fine of up to $1,000, three demerit points and a licence suspension of three days, with higher penalties for repeat offences. Some provinces also have a broader careless driving offence that covers other distractions. Check your province's rules, because they differ in detail.

Legal rules are a floor, not a target. Many employers adopt stricter fleet policies that forbid all phone use while driving, including hands-free, except for emergencies, and require drivers to pull over in a safe place before making or taking calls. They also tell supervisors and clients not to expect immediate replies from people who are driving.

Alcohol

Alcohol slows reaction time, impairs judgement, narrows attention, reduces coordination and makes drivers more willing to take risks. Impairment begins well below the legal limits. Even a blood alcohol concentration (BAC) of 0.02 to 0.05 per cent measurably affects divided attention and tracking, and crash risk rises steeply above 0.05 per cent. Only time removes alcohol from the body; coffee, cold showers and food do not speed it up. On average the body eliminates roughly one standard drink an hour, but individuals vary widely.

Under the Criminal Code, it is an offence to have a blood alcohol concentration of 80 milligrams of alcohol in 100 millilitres of blood (0.08) or more within two hours of driving, and police may demand a breath sample from any driver they lawfully stop, without needing to suspect alcohol. Most provinces also have administrative sanctions in a warn range starting at 0.05, with immediate roadside licence suspensions and vehicle impoundment, and zero-tolerance rules for novice and young drivers and, in several provinces, commercial drivers.

Cannabis and other drugs

Cannabis impairs coordination, reaction time, attention and the ability to judge time and distance. Its effects vary with the product, the dose, how it is consumed and the person. Edible products can take an hour or more to take effect and last many hours, which makes it hard for users to judge when they are fit to drive. Combining cannabis and alcohol is particularly dangerous because the effects add up. Other illegal drugs, such as opioids, stimulants and hallucinogens, impair driving in different ways, and some, such as methamphetamine, can make drivers aggressive and overconfident, followed by severe fatigue as the drug wears off.

Canada's Criminal Code sets blood drug concentration limits for THC, the main impairing component of cannabis: 2 to less than 5 nanograms per millilitre of blood is a less serious offence, 5 or more is a more serious offence, and a combination of 50 milligrams of alcohol per 100 millilitres with 2.5 nanograms of THC is also an offence. Police may use approved oral fluid screening devices and drug recognition experts. Impairment by any drug to any degree is also an offence.

Medications

Many prescription and over-the-counter medications can impair driving: some antihistamines, sleeping pills, muscle relaxants, opioid painkillers, anti-anxiety drugs and some antidepressants among them. Labels often warn about drowsiness or operating machinery. Workers who drive should ask their doctor or pharmacist whether a medication affects driving, especially when starting a new one or changing the dose, and tell their supervisor if they are not fit to drive, without having to disclose the medical details. Employers should make it easy to report this without fear of discipline.

Other distractions and states of mind

Eating and drinking, smoking, grooming, pets loose in the vehicle, unsecured objects rolling around, and passengers who demand attention all distract drivers. So do strong emotions. Anger, grief and stress narrow attention and make aggressive driving more likely. Road rage often begins with a minor incident and escalates when both drivers treat it as a contest. A defensive driver lets the other driver go, avoids eye contact and gestures, and, if followed, drives to a public place such as a police station rather than home or to the workplace.

# Alcohol elimination is slow: rough illustration of BAC over time.
# Peak BAC for an example drinker after several drinks, then about 0.015 per hour elimination.
peak = 0.09          # illustrative peak in per cent BAC
rate = 0.015         # typical average elimination per hour; individuals vary widely
hours = 0
bac = peak
while bac > 0:
    flag = "  over 0.08" if bac >= 0.08 else ("  0.05 warn range" if bac >= 0.05 else "")
    print(f"After {hours:2d} h: about {bac:.3f}%{flag}")
    hours += 1
    bac = round(max(bac - rate, 0), 3)
print("Morning-after driving can still be impaired after a late night of drinking.")

After  0 h: about 0.090%  over 0.08
After  1 h: about 0.075%  0.05 warn range
After  2 h: about 0.060%  0.05 warn range
After  3 h: about 0.045%
After  4 h: about 0.030%
After  5 h: about 0.015%
Morning-after driving can still be impaired after a late night of drinking.

Passengers and co-workers

Passengers can help or hinder. A co-worker who reads the map, watches for signs and handles the phone can reduce the driver's workload. A passenger who argues, shows the driver things on a phone or distracts them with demands adds risk. Crews who travel together can agree simple rules: the passenger handles navigation and calls, nobody shows the driver a screen, and anyone can speak up if they see the driver distracted or drowsy. Speaking up is easier when supervisors have made it clear that it is welcome.