The Permitted Dimension of Guide Sign in Freeway Tunnel Restricted by the Geometric Space of the Tunnel Vault

Table 1

Legends and explanations of the inner outline in Figure 1.

Tunnels	Legend	Explanation	Arc radius
Two-lane freeway tunnel in Figure 1(a)	O1	Center of a tunnel vault circle	—
		Tunnel vault	⟶ R11
	and	Tunnel arch foot	⟶ R12;  ⟶ R12
		Tunnel inverted arch	⟶ R13
Three- or four-lane freeway tunnel in Figure 1(b)	O1	Center of a tunnel vault circle	—
		Tunnel vault	⟶ R21
	and	Tunnel middle part	⟶ R22;  ⟶ R22
	and	Tunnel arch foot	⟶ R23;  ⟶ R32
		Tunnel inverted arch	⟶ R24