Quick Summary:
- Split limits cap injury-per-person, injury-per-accident, and property damage separately.
- Combined single limit offers one shared pot, often more flexible.
- SLI usually increases third-party liability limits, not damage to your hire car.
- Compare your risk, state minimums, and assets before paying for upgrades.
When you arrange car hire in the United Estates, liability insurance is the part that confuses people most, partly because the numbers are shown differently to what many UK travellers expect. Two phrases matter here: split-limit liability and SLI, which usually stands for Supplemental Liability Insurance. To decide whether SLI is a meaningful upgrade, you need to understand what the existing liability limits look like and whether the limits are “split” or “combined”.
Liability cover on US car hire generally relates to injuries or property damage you cause to other people, not damage to the vehicle you are driving. It is separate from collision cover (often called CDW or LDW) and separate from personal accident cover. So even if you have strong collision cover, you can still be exposed on liability if the limits are low.
If you are comparing options and want a general overview of US rentals, it can help to start with a location page such as car hire in the United States, then focus specifically on the insurance section for the vehicle class and supplier you choose.
What “split-limit liability” means in plain English
A split-limit liability policy breaks the maximum payout into separate caps, typically shown as three numbers. The most common pattern is:
1) Bodily injury per person, the most the insurer will pay for injuries to any one individual.
2) Bodily injury per accident, the most the insurer will pay in total for injuries to everyone combined in a single accident.
3) Property damage per accident, the most the insurer will pay for damage to other people’s property in a single accident, for example another car, a fence, or a shopfront.
These are usually written like “25/50/25”, “50/100/50”, or similar. The units are typically thousands of dollars, so 50/100/50 commonly means up to $50,000 bodily injury per person, up to $100,000 bodily injury total per accident, and up to $50,000 property damage per accident.
The key point is that each bucket has its own ceiling. You cannot borrow unused amounts from the other buckets. That is what can make split limits feel restrictive in higher-cost scenarios.
How combined single limit (CSL) differs
A combined single limit, often abbreviated CSL, gives one total liability amount per accident that can be used across bodily injury and property damage together. Instead of three numbers, you may see one figure such as $300,000 CSL or $1,000,000 CSL.
Why it can be better: CSL is more flexible. If the main cost in an accident is property damage rather than injuries, the single pot can be applied where it is needed most, up to the overall limit.
Why it might not matter: if your existing split limits are already high, the flexibility may not materially change your risk. The problem is that “high” depends on the scenario, medical costs, and local legal environment.
How split limits can bite in real-world scenarios
Split limits can leave you exposed in a few common patterns:
Multiple people injured. Even if the “per accident” injury limit looks reasonable, a low “per person” limit can be exhausted quickly for one seriously injured person, leaving the remainder as your responsibility.
One expensive vehicle hit. Property damage limits can be the weak point. Damaging a high-value vehicle, multiple vehicles, or roadside infrastructure can exceed a modest property damage cap.
Mixed losses. If you have both significant injury and property claims, the separate buckets can be individually maxed out, even though the total harm would have been covered under a single higher CSL.
None of this means split limits are “bad” by default. It means you need to read the numbers and imagine what would happen if costs were skewed toward one bucket.
Where SLI fits in on US car hire
SLI, Supplemental Liability Insurance, is typically an optional add-on offered with US car hire that increases your third-party liability limits beyond the basic level. In some cases it may be called LIS, Liability Insurance Supplement. The name and exact structure depend on the rental supplier and the state.
SLI commonly provides a much higher limit, often expressed as a single combined amount, such as $1,000,000, although you should always verify the terms for your specific rental. Importantly, SLI is about claims made by other people against you for injury or damage you cause. It does not normally cover theft or collision damage to your hire vehicle, and it does not replace CDW or LDW.
If you are comparing suppliers, you may see differences in how the basic liability is described and how SLI is presented. For instance, policies and inclusions can vary between big brands such as Hertz car hire in the United States and Enterprise car hire in the United States, even when the vehicle class is similar.
Does SLI always convert split limits into a combined single limit?
Not always. Some SLI products are written as a combined single limit, which can feel like a clean upgrade from split limits. Others may still operate with specific definitions and exclusions. Also, the underlying liability provided by the rental agreement or state requirements may remain split-limit, with SLI sitting on top as excess coverage.
The practical way to judge it is not to assume based on the label, but to look for:
The limit amount, for example $1,000,000.
How the limit is expressed, CSL versus three-number split limits.
Whether it is primary or excess, meaning whether it pays first or only after underlying coverage is used.
Who is covered, for example authorised drivers only.
Territory, typically within the US and sometimes Canada, depending on terms.
How to decide whether SLI is a meaningful upgrade
The goal is to align liability limits with the real financial risk. In the US, medical costs and legal judgments can be high. If the basic liability in your rental is close to state minimums, SLI can be one of the most meaningful add-ons because it targets the area where claims can escalate fast.
Use this checklist when judging whether SLI meaningfully upgrades your cover:
1) Identify the basic liability limits included. Are they split limits like 25/50/25, or something higher? If you only see “minimum required by law”, treat it as a prompt to investigate further, not as reassurance.
2) Compare property damage specifically. Many travellers focus on injury limits, but property damage can be the first bucket exhausted in multi-vehicle incidents or collisions with structures.
3) Consider who may sue. Liability is not just about the other driver. Passengers in other vehicles, cyclists, pedestrians, and property owners can be claimants.
4) Think about where you are driving. Busy urban areas, motorways, and places with higher vehicle values change the risk picture. Even choosing a larger vehicle class, such as a people carrier via minivan hire in the United States, can influence how you view exposure, because you may carry more passengers and drive more miles on longer trips.
5) Check whether your personal policies apply. Some travellers have umbrella liability or motor coverage at home, but it may not extend to US rentals, and it may not cover non-owned vehicles or foreign rentals. You should not assume your existing cover applies without confirming.
6) Balance cost versus downside. Liability claims are low-frequency but high-severity. SLI is often purchased for peace of mind against worst-case outcomes rather than for small bumps.
Split limits vs SLI, a simple comparison
Split-limit liability describes how a liability policy’s maximum payout is structured, with separate caps for injury per person, injury per accident, and property damage per accident.
SLI is an optional supplement that typically increases your liability limit. It may be offered as a high combined limit, but the exact form varies.
So the comparison is not strictly either-or. You can have split limits as the baseline and then SLI on top, or you can have SLI that effectively gives you a large combined limit for the primary exposure. The important part is to compare numbers and structure, not just names.
Common misconceptions to avoid
“SLI covers the rental car if I crash.” Usually false. That is typically CDW or LDW territory. SLI is about third-party claims.
“If I buy CDW, I do not need liability.” False. CDW and liability solve different problems. One relates to the hire vehicle, the other relates to harm you cause others.
“Minimum required by law is enough.” It might be enough for minor incidents, but it is often not designed for major losses.
“All suppliers offer the same liability.” Not necessarily. Even when the legal minimum is the same, included coverage and available supplements can differ between suppliers such as Budget car hire in the United States and others.
How to read the paperwork at pick-up
For US car hire, the counter paperwork or the digital rental agreement is where you can confirm what you are actually getting. Look for terms like “LI”, “LIS”, “SLI”, “ALIS”, “CSL”, or a three-number limit format.
If the document lists a state minimum or shows split limits that feel low relative to your risk tolerance, that is the moment when SLI, if available, becomes relevant. The ideal is to understand this before travel, but verification at pick-up is still worthwhile.
Also confirm that all intended drivers are authorised. Liability products generally apply to authorised drivers only, and unauthorised driving can cause complications in the event of a claim.
FAQ
What does a split limit like 50/100/50 mean on US car hire? It usually means $50,000 bodily injury per person, $100,000 total bodily injury per accident, and $50,000 property damage per accident, each with separate caps.
Is SLI the same as CDW or LDW? No. SLI addresses third-party liability claims. CDW or LDW relates to damage to, or theft of, the hire vehicle, subject to the rental terms.
Is a combined single limit always better than split limits? Not always, but it is often more flexible because one total limit can be applied to injuries and property damage as needed within the same accident.
How can I tell if SLI meaningfully upgrades my cover? Compare the included liability limit to the SLI limit, check whether SLI is expressed as a high CSL, and consider whether property damage or per-person injury caps could be exhausted.
Do US state minimum liability limits differ? Yes, they vary by state and can be relatively low. That variability is one reason travellers review their liability limits carefully for car hire in the United Estates.
