Consider the four points $\text{P, Q, R and S}$ shown in the Greenshields fundamental speed-flow diagram. Denote their corresponding traffic densities by $k_{P}, k_{Q}, k_{R},$ and $k_{S}$, respectively. The correct order of these densities is

1. $k_{P} > k_{Q} > k_{R} > k_{S}$
2. $k_{S} > k_{R} > k_{Q} > k_{P}$
3. $k_{Q} > k_{R} > k_{S} > k_{P}$
4. $k_{Q} > k_{R} > k_{P} > k_{S}$