Queues create many forms of economic waste.
- Longer Cycle Time. It takes longer to reach the front of an extensive line than a small one. Usually, delay costs rise linearly with queue size.
- Increased Risk. Queues increase the transit time through the product development pipeline. When transit time goes up, you're more vulnerable to changes in customer preference, preemption by competitors, and shifts in the underlying technology.
- More Variability. High levels of utilization tend to amplify variability.
- More Overhead. The more projects you have in process, the more you have to track and report the status to your managers. Even worse, your team asks for more progress reports per project because queues lead to long transit times.
- Lower Quality. Queues reduce quality by delaying feedback from downstream processes. If a programmer makes a flawed assumption and must wait 30 days to get this feedback, she'll embed the flawed assumption into 30 days' worth of code. Thus, following a wrong path typically increases exponentially, not linearly.
- Less Motivation. Queues undermine motivation and initiative. When the next process takes a long time, you feel there is little value in hurrying to finish your work. Parkinson's Law explains this behavior.