def _routes_definitions(df):
    """
    Append GTFS definitions for route columns to route dataframe

    Parameters
    ----------
    df : pandas:DataFrame
        routes dataframe

    Returns
    -------
    df : pandas.DataFrame
    """
    if 'route_type' in df.columns:
        routes_route_type = {(0):
            'Street Level Rail: Tram Streetcar Light rail', (1):
            'Underground rail: Subway or Metro', (2):
            'Rail: intercity or long-distance ', (3): 'Bus', (4): 'Ferry',
            (5): 'Cable Car', (6): 'Gondola or Suspended cable car', (7):
            'Steep incline: Funicular'}
        df['route_type_desc'] = df['route_type'].map(routes_route_type.get)
    return df
