Traffic Flow Forecasting for Road Tunnel Using PSO-GPR Algorithm with Combined Kernel Function

Table 1

Traffic flow data by field monitoring of one expressway tunnel.

Number	Day category	Weather	Season	Traffic flow (veh/h)
	Weekdays	Sunny	Autumn	872
	Weekdays	Rainy	Spring	771
	Weekends	Sunny	Autumn	553
	Weekdays	Sunny	Spring	889
	Weekends	Foggy	Spring	438
	Weekdays	Rainy	Winter	490
	Holidays	Sunny	Autumn	681
	Weekdays	Sunny	Autumn	862
	Weekends	Sunny	Summer	504
	Weekdays	Sunny	Spring	880
	Weekends	Rainy	Spring	564
	Weekdays	Sunny	Autumn	858
	Holidays	Sunny	Summer	663
	Weekdays	Sunny	Spring	917
	Weekdays	Rainy	Spring	792
	Weekends	Sunny	Spring	631
	Holidays	Rainy	Spring	571
	Weekdays	Foggy	Autumn	439
	Holidays	Rainy	Autumn	509
	Weekdays	Snow	Winter	481
	Weekends	Rainy	Autumn	505
	Weekends	Foggy	Autumn	382
	Weekdays	Rainy	Summer	574
	Holidays	Sunny	Spring	723
	Weekdays	Rainy	Autumn	675
	Weekends	Snow	Winter	360
	Weekdays	Sunny	Summer	842
	Weekends	Rainy	Autumn	503
	Weekdays	Rainy	Autumn	627
	Holidays	Rainy	Winter	482
	Weekdays	Sunny	Spring	901
	Weekdays	Sunny	Winter	753
	Holidays	Snow	Winter	402
	Weekdays	Foggy	Summer	548
	Holidays	Sunny	Summer	662
	Holidays	Foggy	Spring	469
	Holidays	Rainy	Autumn	504
	Weekdays	Rainy	Autumn	617
	Holidays	Foggy	Winter	402
	Weekends	Rainy	Summer	522
	Weekdays	Snow	Winter	439