Short answer: cyclists who also own automobiles should strongly consider buying additional UM/UIM coverage; this will cover you if you become involved in a crash caused by a motorist and they can’t pay, or reach their policy limits.
While there may be differences between Arizona and Colorado, in this regard, they appear to work the same way. Good review of how auto insurance works (in Colorado!) by The Cyclist Lawyer, Megan Hottman , emphasis added:
MEDPAY coverage –provides medical benefits coverage in any accident involving a motor vehicle, regardless of fault. It usually costs $2-4 per month, and it provides you $5,000 (typically, though it can be more) in medical benefits. This can cover copays or health insurance deductibles, as well as medical bills from the ambulance or emergency room. Your massage, chiropractor, acupuncture, dry needling bills can all be covered too. Any medical expense you incur from the accident is covered, so long as it is medically necessary and reasonable, up to the policy limits.
UM/UIM coverage – if you are hit by a car while riding your bike and the car drives off (aka, a hit-and-run), your Uninsured motorist coverage kicks in. If you are hit by a motorist with minimal insurance coverage (i.e. $25,000, the minimum coverage required in Colorado)[Arizona minimum limits are only $15/$30,000!] and your damages far exceed those limits, you would first recover policy limits from the driver’s insurance company and then you would pursue a UIM (under-insured) claim with your own auto insurer. This can be critical, as often in cyclist-motorist collisions, the cyclist suffers extensive bodily injury and incurs very high medical bills. As a result of their injuries they may also miss a lot of work. UM/UIM coverage will pay for things like medical bills, lost wages, pain and suffering, and more.
In addition, if you want to increase possible coverage, for these or any other claims you may be filing, you can add an “umbrella” policy to all of your existing policies. To add an additional $1 million in insurance protection will run around $300 per year. This will stack on top of any automobile or homeowner coverage you have on your existing policies. In the event of a catastrophic accident involving a cyclist who incurs permanent and life-altering injuries, these umbrellas can be the difference between getting back on one’s feet financially, and filing bankruptcy resulting from the medical bills.
There is a fly in the ointment, though, and I have no idea how to protect oneself from it; as mentioned above, MEDPAY pays regardless of fault. But UM/UIM does not, you have to be able to prove to the insurance company, your insurance company, that you were not at fault for them to pay. Hottman doesn’t discuss what this might mean; she does point out other issues with UIM, e.g. a case where State Farm requested a ridiculous amount of unrelated medical records from their insured. And it’s a weird situation in any event you can find yourself in an adversarial relationship with your own company.
Here’s another re-telling of the same UM/UIM story, this time from California from the bikesiliconvalley.org’s site (emphasis added):
The following recommendations have been provided by our supporters at the Law Office of Daniel H. Rose.
The Law Office of Daniel H. Rose strongly recommends to all California bicyclists that they purchase, as part of their car or motorcycle insurance policy, high limits of uninsured motorist (UM) coverage in case they are ever injured by a motorist…