Section 13

Auditory and vestibular disorders

The hearing standard for drivers is an anomaly among the medical standards describing fitness to drive. All of the other standards are justified by a demonstrated increase in crash risk or the evident danger to road safety of a given medical condition. Thus, although there are no studies establishing that a blind person is at increased risk of crash involvement, it is evident that they should not drive. In contrast, studies have failed to demonstrate that hearing impairment has a significant effect upon the risk of a motor vehicle crash (Dow et al., 2022), and drivers of non-commercial vehicles have never been subject to hearing standards. Opposition to the hearing standard’s role in establishing fitness to drive is often justified by the observation that, if the standard is really a “fitness-to-drive” standard, it would apply to all drivers, not just commercial drivers. Since the hearing standard does not have this broad application, it is argued that it should not be included in the medical standards at all.

Current hearing standards apply only to commercial drivers of certain vehicles — buses, emergency vehicles, taxis, and vehicles carrying dangerous cargoes — as well as Canadian drivers wishing to drive commercial vehicles in the United States. In other words, the hearing standard does not address fitness to drive the vehicle itself, as do all the other medical standards, but rather the driver’s ability to perform the ancillary duties included in their employment. Thus, it is really addressing valid road safety requirements for drivers of such vehicles that are job requirements, not fitness-to-drive considerations.

The Canadian hearing standard (Canadian Council of Motor Transport Administrators, 2021) requires that a driver acquiring or maintaining a Class 2 or Class 4 driver’s licence, those transporting dangerous goods with a Class 1, 3, or 5 licence, or any Canadian driving a Class 1–4 vehicle in the United States must be able to perceive a forced whispered voice at not less than 5 ft (1.5 m) with or without the use of a hearing aid or must have a hearing loss no greater than 40 dB averaged at 500, 1000, and 2000 Hz in their better ear. These drivers should have a corrected hearing loss of no more than 40 dB averaged at 500, 1000, and 2000 Hz and a corrected word recognition score of at least 50%–60%.

The hearing standard is probably the most complicated standard for a driver licensing agency to apply. Although at first view, the hearing standard appears to apply only to drivers who actually drive those particular classes of vehicle, that impression is false.

In Canada, the attribution of a licence for a given class will include all of the classes up to the attributed class. Thus, a Class 3 licence will include Classes 4 and 5, and a Class 1 licence will include Classes 2, 3, 4, and 5, unless the driver has specifically requested the exclusion of one or more of the included classes. As such, a driver with a Class 1 licence who holds all the classes but only drives an articulated truck (Class 1) and never transports dangerous goods or goes to the US in their truck and who has impaired hearing that is below the standard should lose their Class 2 and Class 4 licence, in addition to having their licence restricted as far as transporting dangerous goods and going to the US is concerned. (The fact that they do neither of the latter is immaterial as far as licensing is concerned.)

It should also be noted that even a driver holding only a Class 5 licence (a so-called non- commercial driver) may be required to meet the hearing standard if the pick-up truck or small van that they drive at work is carrying dangerous goods in sufficient quantities to require dangerous cargo warnings.

The Canadian hearing standards for commercial drivers are currently under review and their eventual abolition is a possibility.

In case of doubt or failure on a screening test such as the whisper test, an appropriate audiometric assessment should be performed.

Even if they can be provided with a noise reducer, hearing aids and cochlear implants amplify ambient noise, which may cause fatigue or annoyance. Furthermore, if the devices are not functioning properly, they may mask warning sounds that the driver should be able to hear. If the physician performing the examination thinks the driver is at risk because of their hearing condition, the person should be referred to the hearing professional who has already examined them to assess the permanent or correctable nature of the problem.

Benign paroxysmal positional vertigo is by far the most frequent cause of peripheral vertigo; the disability is temporary, typically lasting less than 2 months. Usually, a person with this type of vertigo is safe to drive unless there is sensitivity to horizontal head movements, in which case the person should be advised not to drive until their condition has subsided or responded to treatment.

Patients with acute unilateral vestibular disorders, such as labyrinthitis or vestibular neuronitis, should be advised not to drive until their condition has subsided and the acute symptoms have resolved. Recovery is progressive over 1 to 2 months. A patient should not drive during this period. Uncommonly, the disorder can recur, but this is not an indication to recommend suspension of the driver’s licence.

The physician should assess whether patients with Menière disease or other causes of recurrent acute vertigo remain fit to drive. Those prone to severe, prolonged attacks or chronic imbalance require evaluation by an otolaryngologist for further investigation and adequate treatment. These patients should be advised to pull off the road at the first sign of an acute attack, until their symptoms subside, and they may wish to avoid driving long distances alone. Menière disease can cause permanent hearing loss; such hearing loss must be assessed for commercial drivers who are subject to the hearing standard.

Tumarkin (non-syncopal drop) attacks can be related to Menière disease. If the person is symptomatic while sitting or the attacks are associated with disabling symptoms such as aura, nausea, or light-headedness, the person should not drive until their symptoms have been investigated and controlled with medical treatment.

Menière disease, labyrinthitis, and vestibular neuronitis can be bilateral and may evolve toward symptomatic chronic vestibular hypofunction.

Most patients with fixed bilateral vestibular hypofunction are safe to drive if they have no acute attacks of vertigo and rely more on vision and proprioception for spatial cues. Those with complete bilateral vestibular loss will have difficulty driving in darkness or on bumpy roads, and they may not be safe to drive under those conditions. In such cases, a road test conducted under those conditions, if available, may be the best indicator of driving ability and safety.