Add getters for traffic volume

src/utils/lam-station.js

@@ -101,6 +101,14 @@ class LamStation {
     return this.avg_speed_dir2;
   }
 
+  get_traffic_vol_dir1() {
+    return this.traffic_vol_dir1;
+  }
+
+  get_traffic_vol_dir2() {
+    return this.traffic_vol_dir2;
+  }
+
 }
 
 export default LamStation;