diff --git a/app/eva_common.py b/app/eva_common.py
index dddfebf..731f891 100644
--- a/app/eva_common.py
+++ b/app/eva_common.py
@@ -1560,7 +1560,7 @@ def gen_inroad_num_problems(road_delay_infos, inroad_static_info_dict, roads_dir
             continue
         lane_info = inroad_static_info_dict[inroadid]['lane_turn_info']
         flow_delay_infos = road_delay.flow_delay_infos
-        max_car_num = max([item.delay_info.car_num for item in flow_delay_infos if item.turn_type in [0, 1]])
+        max_car_num = max([item.delay_info.car_num for item in flow_delay_infos if item.turn_type in [0, 1]]) if flow_delay_infos else 0
         if max_car_num > max_flow_car_num:
             max_flow_car_num = max_car_num
         road_car_num = road_delay.delay_info.car_num