Aggressive parking management programs are possibly the single most effective TDM measure an employer can take to reduce SOV travel. Parking management can take many forms: 1) preferential parking for HOVs/Vanpools (giving carpools or vanpools priority); 2) parking cash-out programs (a cash benefit given to employees); 3) limiting parking supply; and 4) parking pricing (charging the same rate for all vehicles which effectively makes carpools cheaper). Priority parking schemes have a very minimal impact on mode split, but charging for parking can create 20% to 30% reductions in SOV mode share, depending on pricing levels and transit access (Johnston and Ceerla, 1995, pp. 9). Source/Reference: WSDOT, 2000, pp. 29-30.