The economics of shovel waiting vs truck waiting
Mining researchers have debated this for decades, and the answer is remarkably consistent. A waiting truck is cheaper than a waiting excavator. Why? An excavator is the production engine of an open cast mine. It is one of the most expensive assets on site, with high ownership costs, high fuel consumption, and a production rate that directly determines how many tonnes can be moved. If an excavator is waiting for trucks, production stops. If a truck is waiting for an excavator, production continues the moment it is loaded. This is why many mine planning studies recommend keeping excavators busy, even if it means trucks spend some time in a queue. That doesn't mean long truck queues are acceptable. Excessive queuing increases cycle time, fuel consumption, tyre wear, and operating cost. The objective is to keep the shovel digging and keep truck queues short. That balance is where the lowest cost per tonne is achieved. Reference: Principles discussed in surface mine fleet optimization research by SME, Caterpillar performance studies, and Hustrulid & Kuchta's Open Pit Mine Planning and Design.















































































