If velocity of traffic is taken constant. The angular momentum 
    can be considered due to 3 components.                
(1)     Due to earth (upwards)
(2)     Due to (A) (upward)
(3)     Due to (B) (downwards)

when A goes to right magnitude of $\overrightarrow{\mathrm{L}}$ due to it increases        
when B goes to left magnitude of $\overrightarrow{\mathrm{L}}$ due to it decreases        
∴ Δ $({\overrightarrow{\mathrm{L}}}_{\mathrm{A}}+{\overrightarrow{\mathrm{L}}}_{\mathrm{B}})$ is in upward direction and as Δ $({\overrightarrow{\mathrm{L}}}_{\mathrm{A}}+{\overrightarrow{\mathrm{L}}}_{\mathrm{B}}+{\overrightarrow{\mathrm{L}}}_{\mathrm{earth}})$ = 0 
∴ ${\overrightarrow{\mathrm{L}}}_{\mathrm{earth}}$ is downward
∴ ω_earth decreases  ⟹  length of day increases