Which intersection control works best:  a traffic circle, a four-way stop sign, or a traffic cop? Assume an orthogonal four-way intersection with regular but not grid-locked traffic, and that everyone knows and obeys the rules of the road. This is an interview question I read about today.

Like many interview questions, it has a goal: to determine the interviewee’s management style. Most of us want to work for managers who choose the traffic circle, which allows the most autonomy and decision-making for the cars (workers) with the least explicit control. Rule-based managers like the stop sign, which is less ambiguous, while authoritarians want (to be) the cop. In some cases, of course, different management types may be more appropriate. There is also a right answer*, for expediting traffic flow at least.

When I was interviewing engineers, back in the day, I used to like to ask, Why is a manhole cover round? The more tense the candidate, the more this question would be resented, but that’s not why I asked it. I just wanted to find out how creative they were. There are many, many answers. Just think about manufacturing, shipping, moving, and installing a manhole cover, as well as what it’s covering: the circle is best in every case.

A friend who worked in management consulting told me that interviewers would ask a candidate to estimate something, to find out both how she thinks and what she knows. Our family occasionally used this as a game at the dinner table. For example, someone might say, I wonder how many pet dogs there are in the US? Then we would start to figure out what we needed to know, and guess the numbers. For this particular question, you need to know the population of the US, how many households that represents, what percent of households have a dog, and how many dogs each has on average. If you work together, as a discussion, an alert group can usually do pretty well by talking it through. Check the answer on the Internet–after dinner!

Dinner with the family is usually less stressful than an interview, though I actually enjoy an interview most of the time, especially one with a chance to apply my brain to a creative question.

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* Traffic circle keeps traffic moving best.