O.R. at the blood donor session

When I taught queue models in O.R. at the university I encouraged students to give blood at the regular donor sessions held on campus. It was a good example of queues in series -- arrive -- register -- health check -- give blood -- refreshments, and I urged the students to observe and consider how the system could be improved.

Yesterday when I gave blood, I arrived before the system had reached a steady state and there was little delay. Wonderful! As I lay on the couch, it was possible to watch the donor next to me and the machinery used to shake the blood. The plastic bags holding the donated blood rested on a tray which was programmed to rock. What was odd was that the rocking was intermittent. Up, down, up, down, pause. Repeat. Someone had designed it so that it rocked twice and then paused. Why? Was this an optimal way of rocking the blood? Someone had designed the mechanism, and that design had involved finding a numerical solution to "Rock N times, at rate R per minute, pause S seconds"

How many items make a pack?

From time to time, I observe a package or a product in a shop or elsewhere, and wonder why the manufacturers have selected a particular size or number of items.

On my website, there are pictures from the ROCARO conference in Niamey in 2004, including a picture of a beer bottle holding 48cc. Why 48?

The paper towels in the washroom here come in packs of 180 towels. Why 180?

British food packaging is plagued with anomalous sizes. Jam, marmalade and numerous other items are sold in packs weighing 454gm or 340gm (equivalent to 1 pound, or 12 ounces). Flour is sold in bags weighing 1.5kg -- a reminder that it was formerly sold in bags weighing 3 pounds (why 3?)

For the final consumer, these assorted sizes are little more than an irritant; but within a supply chain, they can be more serious.

Now I shall start to collect and report odd-sized packs.

Designing road markings

I am someone who frequently asks the question "Why?" about the design of everyday objects, because of the interplay between design and operational research. On my way to the office today, I noticed that one of the advanced stop lines for cyclists seemed much larger than others that I encounter. So I asked myself "Why is it that size?" and then speculated about the optimal size for such a road marking.

The wonders of Google led me to a website from the UK Department for Transport, which says that the "cycle reservoir should be between 4m and 5m in depth. If the reservoir is shallower than this cyclists can feel intimidated by the close proximity of the vehicles queuing behind them. If the reservoir is deeper than this, motorists may feel encouraged to encroach into it." So the design is based on psychology, which links to some of my earlier blogs here. It is reassuring that someone has thought about the design and suggested guideline measurements.

So if you see me around Exeter with a 4metre tape measure, you will know that I am checking the roads!

Think of the user!

Good O.R. has to be implemented. Period. Full stop.
So, at some stage, someone needs to think of the person who will use the results. The problem may have been presented by management, and the person who pays for the work is in the management hierarchy, but the person who actually uses the results is probably not in management. Which is why implementation is important.
I have linked implementation and design before, but over the Christmas holiday we had experience of both good design (implementation) and bad.
Let's start with the bad news. We bought a new set of Christmas lights to make an arch around the front door. They came with an integral control box which had one button only. Repeated pressing of the button cycled through several patterns of flashing lights, with one where all bulbs stayed on all the time. So we put the string of lights up, switched on and discovered that the default was a pattern which faded and flashed -- too garish for us. So we cycled and selected the constant selection. Then we switched off, to put the string onto a time switch. When it came on, we were back to the default. As a result, at some stage every evening, yours truly had to press the button to select our favoured setting. With a little forethought, the designer could have ensured that the setting that had been selected became the default one for the next off--on sequence ... because that is what the user had expressed a wish to show what was wanted.
The good news was that Tina was given a DAB radio. Plug it in, switch it on, and set up the controls. It was extremely easy, with clear instructions, designed with the user in mind. Full marks for those at "Pure" for thinking of the user.

Operational Research and Design

One of the subject headings in the International Abstracts in O.R. (IAOR) is "Design". Over the years, there have been comparatively few abstracts which were classified under this heading. I wondered why. What sort of papers would be classified as "O.R. in Design"? One tends to think of design in connection with small (comparatively) items or matters, when one is not concerned with aesthetics. Things like household equipment, the layout of roads, small engineering items. A useful text is The Design of Everyday Things by Donald A Norman -- which doesn't mention O.R. but does discuss optimality quite frequently. But this aspect of design does not lead to academic papers. Manufacturers employ designers to make money, not to produce learned papers. Look at the jets in the rotor of a dishwasher; someone has designed them, found the best angles, positions and sizes, in order to efficiently and cheaply carry out a dishwashing cycle. Hard work -- hard O.R. work -- but not worth writing about. Sometimes the results of design are commercial secrets. When I was recently out of my postgraduate training, I went on a site visit and asked about a piece of equipment on the production line. Had the company patented it? No, because a patent would be visible to their rivals.

But sometimes one wishes that the results of design as the result of a modelling process could be made public. By doing that the benefits of one person's analysis could be usefully shared. I come across such an example regularly. What is the optimal separation between cycle racks? By the swimming pool, there are six racks, at 45cm apart. The outermost racks are therefore 225cm apart, and one can park seven bicycles in the space. Near the office, there are four racks, 100cm apart. Two bikes can be parked in each gap, so in 300cm there are eight bikes. Which is better?