def is_large_truck(df):
    """Return if vehicle is a large truck, per NHTSA convention."""
    yr = df['YEAR']
    body = df['BODY_TYP']
    tow_veh = df['TOW_VEH']
    return yr.between(1975, 1981) & (body.between(53, 59) | (body == 60) &
        (tow_veh == 1)) | yr.between(1982, 1990) & (body.isin([70, 71, 72, 
        74, 75, 76, 78]) | (body == 79) & tow_veh.between(1, 5)) | (1991 <= yr
        ) & (body.isin([60, 61, 62, 63, 64, 66, 67, 71, 72, 78]) | (body ==
        79) & tow_veh.between(1, 4))
