According to Volvo Trucks North America…
Volvo’s family of D11, D13 and D16 engines can be ordered with an optional Low NOx Idle, or LNI, feature. With LNI, Volvo engines are certified to emit 30 gr/hr or less of NOx while idling. California regulations prohibit trucks which do not meet this standard from idling for more than five minutes. Pennsylvania and New Jersey have adopted the requirement and other states are considering it.
“As part of our environmental core value, Volvo has always promoted turning the engine off when a truck is not in use to reduce emissions and to conserve fuel,” said Matt Kelly, Volvo’s executive director – marketing. “However, it may be necessary to idle the engine while parked for a prolonged period in order to provide a comfortable environment to the driver who may be resting in the truck, such as during particularly hot or cold weather.”
Volvo’s LNI solution involves idling at a low 700 rpm, while also employing a low level of exhaust gas recirculation. This reduces fuel consumption compared to higher idle speeds, and lowers NOx emissions. It also provides faster engine warm-up, so the truck can be driven sooner after a cold start, which saves time and fuel, all with lower emissions. Volvo engines can be safely idled for extended periods of time.
Source: Volvo Trucks North America