sentences:  In order for NTE standards to apply, the engine needs to remain within the NTE zone (limits include operation at a minimum of 30% of rated power) for at least 30 seconds.Concerns arose that performing this action could prove to be difficult, as each time the driver removes the foot from the accelerator pedal, or shifts gears on vehicles with manual transmission, the engine leaves the NTE zone.In urban or suburban driving, this happens relatively often, to the point that NTE standards are applicable only a very small portion of the operation 
  or, in some cases, not at all.