For cables in tunnels, this is the inner width of the tunnel (only applicable for rectangular tunnels).

For cables in troughs, this is the inner width of the trough.

Symbol
$w_{\mathrm{t}}$
Unit
m
Used in
$A_{\mathrm{t}}$
$Di_{\mathrm{t}}$
$Do_{\mathrm{t}}$
$H_{\mathrm{tc}}$
$p_{\mathrm{tr}}$
$\phi_{\mathrm{b}}$
$T_{\mathrm{tr}}$