Car rentals for car-free people

One of the things that makes car-free living in the city bearable is the occasional long weekend out in the country. Carsharing services like Zipcar and Hertz 24/7 have made trips like these vastly easier and more convenient but I still find myself needing to do a traditional car rental a couple of times a year – especially when I'm traveling. What astounds and irritates me is how there's almost no information out there about how do handle liability insurance when you don't already own a car. 

BOTTOM LINE (for Americans renting cars in the USA):

1. If you don't own a car (and ergo have no insurance), you should probably take the Liability Insurance Supplement insurance from your rental car company. 
2. Most credit cards offer coverage for the vehicle itself, but none offer liability.
3. If you rent cars more than 30 days a year, call an insurance broker and get a "non-owners auto policy" for when you rent cars. 

When I've talked with other car-free folks about this I'm surprised by the number who think, "oh, my fancy credit card covers all of that for free..." They're wrong. No credit card offers liability insurance, not even American Express' fancy supplemental program does. Those programs cover the cars, but I'm way more concerned about other people's medical bills in the event that I'm found even partially at fault. State minimums basically cover a broken arm and not much more.

Liability NOT INCLUDED!

I'm not a lawyer or an insurance expert but here's what I've found:

• Some states require rental car companies to carry the state-mandated minimum of liability insurance for people who rent cars there. 
• For New York state, that comes out to $25,000 of personal injury with a maximum of $50,000 per incident. (link has lots of other helpful info)
• For Massachusetts, those numbers are $20,000 / $40,000
• For California, the rental car companies are NOT required to include any liability coverage in their rental fees.
• The rental car agencies seem intentionally cagey about listing which states require them to provide liability coverage as part of their base rates. I've been having good luck spot checking states by just googling, "does {state} require rental car companies to carry liability insurance?" 
• Your homeowners insurance company might be able to add an umbrella liability policy that will offer liability coverage when you're driving a rental. 
• I've heard that filing a claim with your credit card requires an huge amount of paperwork versus filing a claim when you've used the rental car company's insurance.
• You can get a "non-owners auto policy" from an insurance company but it likely won't be worth it unless you rent a car for more than 30 days a year. Geico, for example, quoted me $400 a year for $500,000 of liability coverage. 

State mandated liability insurance levels (from hertz's website)