def join_veh_len_to_BSM_df(df_BSM_name, veh_len_df_name):
    """Join vehicle length column to main BSM df."""
    df = df_BSM_name.merge(veh_len_df_name[['Type_ID','Length (ft)']], how='left', left_on='Type', right_on='Type_ID')
    df = df.drop(['Type_ID'], axis=1)
    #print(df.head())
    return df