IF they follow some safety rules like a truck walk around before moving which is a good idea for all, then it isn't likely to happen to them anymore than a driver who can hear. Ever yell at a UP diver once the engine starts? They can't hear you.
IF the driver can pass a D.O.T. physical and demonstrate the capabilities and skills to drive then let them. But there is another factor here which has to be addressed and that is customer communications. UPS runs trucks on a tight schedule. The drives literally drive like mad to make scheduled stops and deliveries. They are timed and the company knows where their drivers are within a few minutes. I suppose communications can be worked around. The driver would need to have the skills to communicate quickly. Many deaf persons can do so. For example if the driver is also illiterate then forget it.
Deafness is a disability and disabilities come in all forms. Many walking disabled are out there with disabilities others can not see. I'm partially deaf myself but I could get in an 18 wheeler right now and drive it if not for my other medical disability for which I can not work. I could still drive an 18 wheeler but not safely.
My last job was medical facility building maintenance. I don't mean janitor I was skilled labor in Boiler Operations, Electrician, HVAC Tech, and plumbing. But my concentration capabilities and tolerances to certain audio and visual stimulation say I can no longer work. Actually through compensating I stayed a few months longer at my job than what was safe for all concerned. I also have to understand the fact I may at any time have to surrender my drivers license for my car if some seizure activity which stays in by shoulder blades so far moves down into my elbows and hands.
You have to know and understand your limitations that is your responsibility to be open and honest about them when seeking employment. Oh yea I'm also technically blind in one eye. Two eyes with vision never at the same time. I'm a sensory system wreck :>} One other point here is this. Vestibular {Hearing} Disorders can mean other issues like poor concentration or poor sensory processing in other areas. That needs to be checked out as well and be a factor in hiring a driver. That should be cause not to hire as well.
If the UPS driver has visual impairments like single vision and deafness that should be enough to say no hire. The brain is pretty amazing at compensating but compensation can only do so much as it starts putting the brain in conflict. It's like a computer only so much data can be processed and so many functions can be done at one time. Compensation after an extended time frame can also bring on more serious issues as my brain told me in a very rude way.
I'm against the ADA on principle that government has no right managing someone else's business and ADA laws should apply only to taxpayer funded facilities and government venues. IOW City Hall should be built accessible to persons in wheel chairs or blind etc. But government should not be able to force Joe's Diner to do the same as adaption can be impractical in many cases and costly in most. I say this as a caregiver of 20 year to a quadriplegic. We give business to those who do in appreciation but we don't demand anyone build wheelchair ramps etc.
Uh okay, you made that up.
Let's see some documentation, please provide us a link here.
Thanks.