A process in which the extent of vascular smooth muscle contraction is reduced. Vascular smooth muscle relaxation is mediated via a decrease in the phosphorylation state of myosin light chain. This can be achieved by removal of calcium from the cytoplasm to the sarcoplasmic reticulum lumen through the action of Ca2+ ATPases leading to a decrease myosin light chain kinase activity, and through calcium-independent pathways leading to a increase in myosin light chain phosphatase activity.