Under what condition is property used by the NJ Highway Authority taxable?

The correct understanding of the condition under which property used by the New Jersey Highway Authority is taxable revolves around how the property is utilized. Property owned by the NJ Highway Authority is generally exempt from taxation when it is used for projects that serve public purposes and are related to transportation infrastructure. This exemption aligns with the idea that properties used for public projects support the common good and efficient operation of public facilities.

When such properties are not utilized for public projects—perhaps if they are used for commercial purposes or other non-qualifying activities—they can become subject to taxation. This reflects the principle that property should contribute to local tax revenues when it is not serving its intended purpose in the public interest.

The other options do not accurately represent the conditions under which these properties become taxable. For instance, the idea that property is "always taxable" does not recognize the significant exemptions in place. Similarly, the notion that residential use or property purchased after a specific date triggers taxation fails to address the core principle regarding the actual use of the property in question. Therefore, the focus on the property's use for projects becomes the definitive factor in determining its taxability.