Abstract: Method of operating vehicle management systems are disclosed in particular for the delivery of goods which potentially degrade during a journey for example concrete. The method includes registering a different delivery time slots for multiple vehicles to a location. Using GPS to determine the locations of the vehicles on their journeys and estimating the expected arrival times at the delivery location for the vehicles. If one vehicle will be late and another will be early swapping the delivery time slots and if the one vehicle has goods which, from monitoring a variable of the goods, can be seen to be unsuitable for delivery within the time delivery window for that vehicle, swapping the time delivery slot with another vehicle by directing that vehicle to a holding area.