Appendix 3.7	Detailed Calculation of In-Tunnel Air Quality
	for the Full Enclosure at Castle Peak Road viaduct
		-	Worse case
Tunnel Parameter
Tunnel length (m), L		=	175
Tunnel height (m), H		=	5.5
Tunnel width (m), W		=	20
Tunnel size (m2), At		=	H * W
			110
Equivalent diameter (m), dt		=	(4*At/p)^0.5
			11.83455
Effective length of the tunnel (m), Le		=	L + 2*3*dt
			246.0073
Emission Data
			Traffic Breakdown (%)
	Traffic flow (veh/hr)		Petrol	L.Diesel	H.Diesel	LGV	HGV
Tunnel traffic	2410		43	32	25	0	0
Q (veh/hr)			1030	781	600	0	0
			Petrol	L.Diesel	H.Diesel	LGV	HGV
Emission Factor (g/km) - EURO3			0.71	1.54	6.8	1.23	3.84
Weighted NOX E.F. (g/km/veh)		=	2.494227
NO2 emission factor per unit length (g/m/s), w				=	0.000334
Vehicle Data
Nominal dimensions of vehicles are given in Transport Planning and Design Manual, Vol. 2 as:
			W	H	L
	Pertol		1.7	1.5	4.6
	L.Diesel		2.1	1.6	5.2
	H.Diesel		2.5	4.6	16
	HGV
Nominal cross-sectional area (m2)		=	(1.7*1.5*(0.43)+(2.5*4.6*0.25)+(2.1*1.6*0.32)
		=	5.039427
Number of lanes per direction, nl		=	2
Equivalent cross-sectional area for each direction (m2), Av					=	10.07885
Equivalent diameter of vehicle (m), dv		=	(4*Av/p)^0.5
		=	3.582291
Equivalent length of each vehicle (m)		=	(4.6*(0.43))+(5.2*0.32)+(16*0.25)
		=	7.631071
Distance between vehicle (m)		=	1	(worst case)
Head to head distance on a lane (m), l		=	8.631071
Traffic density (traffic flow /s), N		=	0.669444
Average vehicle speed (m/s), v		=	l*N/(2*nl)
		=	1.444506
Diffusion Parameters
Reynolds number, Re		=	(v*dv)/s		where s = 15.6*10^-6
		=	331707.6
According to Figure 16 (Ohashi and Koso)
Since	l / dt	=	0.729312
D / (N * dt^2 * Re^0.13)		=	0.15
Longitudinal
diffusion coefficient (m2/s) , D		=	0.15 * (N * dt^2 * Re^0.13)
		=	73.41878
Maximum Concentration of NO2
Cmax (µg/m3)		=	w * Le^2 / (8 * D * At)
(without background)		=	312.8143