These are the conditions as published by Dollar
I know it's long but it answers all your questions
Also look for the gold or all inclusive packages they will often work out cheaper and you'll have peace of mind that it's all covered

Optional Protection Package: At the time of rental, DOLLAR offers for purchase at the option of the renter, Loss Damage Waiver ("LDW"), Personal Protection Plan ("PPP"), Protection Plus (PP), Personal Accident Insurance ("PAI"), Personal Effects Insurance ("PEI"), Supplemental Liability Insurance ("SLI") and Uninsured and Underinsured Motorist Protection ("UMP"). The per day cost, coverage, provider and availability vary by location, vehicle category and rate. Please refer to the location's Local Policy to determine whether SLI is required for travel into Canada and the cost of such coverage. The optional products offered by the rental company may duplicate coverage provided by the renter's personal automobile insurance or insurance the renter may have through another source. Purchase of optional products is not required to rent the vehicle. Separate brochures available at the rental location summarize the optional products. We charge a per day fee for each day or part of a day the vehicle is rented for any optional products you select.

Loss Damage Waiver ("LDW"): If the renter purchases one of the optional LDW plans, DOLLAR will agree to waive the renter's responsibility for loss or damage to the vehicle in full or in part (depending on the LDW plan accepted). LDW is not insurance.

LDW does not apply if: (1) the renter uses the vehicle in violation of the rental agreement; (2) the renter fails to remove the keys, or close and lock all windows, doors and trunk, and the vehicle is stolen or vandalized; (3) the renter fails to notify us and the police immediately after the loss; and (4) the renter fails to pay the charges under the rental agreement; or (5) other exceptions as allowed by the applicable state or provincial law.

Before deciding whether to purchase LDW, the renter may wish to determine whether their own automobile insurance or credit card agreement provides coverage for rental vehicle damage or loss and determine the amount of the deductible under their own insurance coverage. The purchase of LDW is not mandatory. LDW is not insurance.

Personal Protection Plan ("PPP"): PPP includes Personal Accident Insurance ("PAI") and Personal Effects Insurance ("PEI") and where offered must be purchased together. PPP is not offered in Canada

PAI provides benefits to the renter and the renter's passengers for accidental medical expenses, ambulance expenses and accidental death benefits during the rental. If this optional coverage is purchased by a renter, the renter is covered twenty-four hours a day for all accidents, whether the renter is actually in the rental vehicle or not at the time of the accident. Passengers in a DOLLAR vehicle are only covered for accidents occurring while the passengers occupy the DOLLAR vehicle.

PEI insures the personal effects of the renter and any member of the renter's immediate family traveling with the renter. A member of a renter's immediate family must permanently reside in the renter's household. If this optional coverage is purchased by the renter, PEI covers only personal effects with which the renter or immediate family member are traveling. The total maximum coverage is $1,500. PEI pays covered claims even if the renter's homeowner's policy provides coverage.

Supplemental Liability Insurance ("SLI"): Where available, and for an additional daily charge, a renter may purchase SLI at the time of rental. If accepted, SLI provides the renter or any additional authorized drivers listed in the rental agreement, with automobile liability coverage against third party claims (excluding claims by the renter's and any additional authorized driver's family members related by blood, marriage or adoption and any other person residing with the renter or additional driver) for bodily injury, including death, and property damage resulting from an automobile accident in the DOLLAR vehicle, during the rental period, in excess of the coverage provided under the rental agreement up to a maximum protection of $1,000,000 combined single limit (CSL) per occurrence. The availability, cost and coverage can vary from location to location depending on the program details. Check with the rental location for details of their program. SLI does not provide coverage for uninsured and underinsured motorist protection except in New York. SLI does not apply in Mexico. SLI is not offered in Canada.

OPTIONAL LIABILITY COVERAGE IS SUBJECT TO SPECIFIC BENEFITS, EXCLUSIONS, LIMITATIONS AND EXCEPTIONS WHICH ARE SUMMARIZED ON THE SEPARATE BROCHURES AVAILABLE AT THE RENTAL LOCATIONS. See the Notices below:

If you purchase SLI in New York: In New York, for an additional daily charge, two SLI products may be available: (i) SLI with an uninsured/underinsured motorist protection up to $1,000,000 Bodily Injury per accident limit; and (ii) an SLI with a $100,000 Bodily Injury each person/$300,000 Bodily Injury per accident limit (a "Supplemental Tier").

If you rent in Texas: The renter may not need the automobile insurance offered by the rental car company. The purchase of automobile liability insurance is not required as a condition of renting an automobile. This insurance does not apply to any bodily injury or property damage arising out of the use or permitting the use of a rental vehicle by any driver while under the influence of drugs or alcohol in violation of the law.

Uninsured and Underinsured Motorist Protection ("UMP"): If the renter purchases SLI, the renter may have the opportunity to purchase UMP. UMP provides the renter; any authorized additional driver and anyone else occupying a DOLLAR vehicle while operated by the renter or an additional authorized driver, with coverage for injuries and damages caused by an owner or driver of an uninsured or underinsured third party vehicle. This coverage is excess above the minimum financial responsibility limits for uninsured and underinsured motorist coverage required by law, if any. UMP provides coverage for the difference between any uninsured and underinsured motorist coverage available to the renter in the rental agreement, if any, up to a maximum of $1,000,000 combined single limit (CSL) per occurrence. UMP is included with the SLI purchased in New York and may not be offered or sold separately. UMP does not apply in Mexico. UMP is not offered in Canada.

Protection Plus ("PP"): In Canada, where available, if the renter purchases PP, it will provide limited benefits to the authorized driver and passengers of the vehicle during the rental for accidental medical expenses, ambulance expenses and accidental death, repatriation, rehabilitation, legal defense, emergency road service and mechanical breakdown towing benefits, and loss to personal belongings if certain terms and conditions are met.