$A_a$	area of the nominal contact surface (${\mathrm{m}}^2$)
$A_c$	area of the contour contact region (${\mathrm{m}}^2$)
$A_r$	area of the real contact region (${\mathrm{m}}^2$)
$A_{\mathrm{vent}}$	area of the ventilated surface of the disc or drum (${\mathrm{m}}^2$)
$b_0$	parameter of the reference-surface curve (dimensionless)
$c$	specific heat ($\mathrm{J} {\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$)
$d$	thickness ($\mathrm{m}$)
$d_r$	diameter of an average spot of the real contact region ($\mathrm{m}$)
$f$	coefficient of friction (dimensionless)
$h$	coefficient of heat transfer ($\mathrm{W} {\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$)
$h_{\max }$	maximum roughness height on the friction surface of the disc or drum (($\mathrm{m}$))
$HB$	Brinell hardness ($\mathrm{Pa}$)
$K$	thermal conductivity ($\mathrm{W} {\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$)
$n$	number of braking in RST brake mode
$p$	contact pressure ($\mathrm{Pa}$)
$p_0$	nominal value of the contact pressure ($\mathrm{Pa}$)
$q$	specific power of friction ($\mathrm{W} {\mathrm{m}}^{-2}$)
$q_0$	nominal value of the specific power of friction ($\mathrm{W} {\mathrm{m}}^{-2}$)
$r_{av}$	average rounding radius of roughness on the friction surface ($r_{av}$)
$t$	time ($\mathrm{s}$)
$t_b$	time of performance of all RST mode of braking (s)
$t_c$	cooling time at acceleration (s)
$t_i$	time of pressure increase (s)
$t_s$	time of braking (s)
$T$	temperature (${}^{\circ }\mathrm{C}$)
$T_0$	initial (volumetric) temperature (${}^{\circ }\mathrm{C}$)
$T_f$	flash temperature (${}^{\circ }\mathrm{C}$)
$T_m$	mean temperature (${}^{\circ }\mathrm{C}$)
$T_{\max }$	maximum temperature (${}^{\circ }\mathrm{C}$)
$V$	velocity ($\mathrm{m} {\mathrm{s}}^{-1}$)
$V_0$	initial velocity ($\mathrm{m} {\mathrm{s}}^{-1}$)
$W_0$	initial kinetic energy ($\mathrm{J}$)
$z$	axial coordinate (($\mathrm{m}$))
Greek Symbols
$\nu$	parameter of the reference-surface curve (dimensionless)
$\rho$	density ($\mathrm{kg} {\mathrm{m}}^{-3}$)
Index
upper $k$	number of a stage of braking
lower $l$	number of the main ($l=1$) and frictional ($l=2$) elements of the friction couple