System up and running: From first entry to last finisher, the London Marathon computer holds the records. Martin Whybrow reports

AT ABOUT two o'clock next Sunday afternoon there will be an average of nine runners per second crossing the finish line at the end of the London Marathon. In all, there are 35,750 runners registered this year, making it the largest to date. Not only is it a wonderful spectacle, but it is also a logistical headache in terms of monitoring and timekeeping.

The computer systems are in the hands of Unisys, as they have been for the last three years, with Citizen this year's official timekeeper. On the day, Unisys will have around 30 staff in place and networked terminals around the course. Being a one-off event, there is no chance to practise, and it can only start to set up its systems at the finish line on Tower Bridge from around 10 o'clock the previous evening, when the bridge is closed to traffic. It is also a high-profile event, so any failure would have an equally high profile.

In fact, the organisational work really starts around August of the preceding year with the arrival of the first of the 80,000-plus entries. The details are passed to the marathon organisers and those selected are put on to a database. Acceptance letters and registration forms are generated from this. A host of information is held for each runner and can be sorted on any criteria.

Part of Unisys's job is to provide information to the media. If, for instance, the Scunthorpe Evening News wants to know the names of any runners from Scunthorpe, this can be extracted. On the day, the BBC's Grandstand studio is provided with on-line access to the database. When runners appear on the television screen, the numbers on their shirts can be keyed in and the data displayed just for the commentator or on screen for the viewers in the form of a graphical display. When David Coleman recognises the 60-year-

old grandmother Elsie Smith from Worksop, it is not because he has memorised her details beforehand. The press centre in the Tower Hotel is provided with a link; so too is St John Ambulance, and the organisers' central control centre in County Hall.

Unisys also has the task of trying to keep track of the thousands of runners. They are each issued with unique bar codes that are attached to their race numbers. A problem that the timekeepers encounter every year is that of the fraudulent runner who completes all or some of the course and then hands in a meaningless bar code off the previous night's tin of baked beans.

When a runner crosses the finish line, an electronic pulse is generated that records his or her time. The bar codes are collected, put on to a spindle and read. Runners are directed into funnels and the pulse is matched to the bar code to produce a time for each participant. The idea is to line the runners up in the order they finish, so that 10 runners can be matched with 10 consecutive time pulses. As one funnel is filled up, another is opened and so on, on a rotating basis.

The theory sounds simple, but the sheer volumes crossing the line at the peak time make this a complicated task. The natural reaction of people who cross the line after 26 miles is to stop. London Marathon staff await the finishers to try to shepherd them onwards and into their respective funnels. Some runners do not, of course, make it to the finishing line; their bar codes and details are captured around the course where possible, but some people invariably wander off or get carried away unnoticed, their bar codes unread.

The task of timekeeping should be simplest for the elite runners, purely because the numbers are more manageable. There are, in fact, five separate, staggered races so that different categories of runners should finish at different times. Last year, however, the elite women ran slower than expected and the elite men ran faster, so the two sets crossed the finish line at around the same time. This meant that they became mixed up in the wrong funnels; the task of ratifying the results took almost half an hour and the BBC, which covers the race from start to finish, managed to completely miss filming the winner of the men's race as he crossed the line.

Another problem is that many runners do not agree with their allotted times. The organisers film the finish line themselves so that any disputes can be resolved after the race. However, the primary cause of the disputed times stems from the fact that in the main race the numbers are so great that it can take some participants up to 15 minutes to even reach the starting line. Many runners start their watches at the moment they cross this line, whereas the bar code technology necessitates that the official timing starts at the moment the race itself begins.

For this reason, the introduction of transponder technology is being considered for the future. Each runner would carry a device that emits a unique pulse. This pulse could be received at the start and finish of the marathon, to provide a specific time for each runner. It has already been used successfully in motor sports and could mean the end of bar codes, funnels, and the baked bean merchants.

(Photograph omitted)