Why the ICC light regulations are what they are

The ICC and its officials, it would appear from events of recent days, can't ever get it right. First, they are roundly criticised for going off for bad light too readily in the second Test between England and Pakistan in Southampton.

Then, after the third day's play in the third Test at the same venue, having played on to make up for lost time on a rain-affected day, Dom Bess says the light was poor enough to be dangerous. Playing on that day seemed like a corrective response to the earlier criticism, with a renewed resolve to get as much cricket in as possible, although Bess didn't think it was the umpires over-reacting. It won't be forgotten that three catches were shelled in quick succession in that period by England.

That has brought the ICC's bad light regulations into scrutiny, something that happens so often now, we're all familiar with the key bits of playing condition 2.7.1; the umpires alone decide if it is "dangerous or unreasonable" for play to continue, but that play shouldn't stop "merely because [conditions] are not ideal."

Given that it is humans ultimately making the decision, there's not going to be one standard interpretation of 'ideal'. Floodlights bring another variable to a decision that is guided - but not dictated - by light meters: why not just play on?

The answer to that lies in trials conducted by the ICC in March 2011 in Dubai, but also replicated at four venues in England the same year, and at the Gabba in 2012. The previous October, amendments to the laws of the game had left umpires as the sole decision-makers on bad light, without needing to consult the batsmen. At an ICC meeting a fortnight before that, the ICC's then GM cricket David Richardson had said, "There is a clear instruction to match officials that the players should only go off the field when conditions are considered dangerous or unreasonable. In addition, players should not go off the field when the ground floodlights are switched on and these were deemed before the series to be adequate."

The ICC doesn't often get credit for the research-based findings that underpin the game's on-field developments. Their work with academic and science institutes on illegal actions, or in convincing the BCCI of the viability of DRS tools, for example, flies under the radar. In that light it was no surprise they set up these trials, the aim of which was to establish the appropriate minimum levels of light required for play to reasonably and safely continue in Tests, while also assessing the impact of floodlights. The key finding was that there is definitely a level of light beyond which it is unsafe to continue playing even under floodlights with a red ball. Results from England and Australia corroborated that finding.

The Dubai trials involved cricketers from the ICC Academy (in England and Australia, county and state cricketers took part) and took place on two late afternoons in March, starting each day in the post-tea session - at 4.15pm - in sunshine. An established lighting company was contracted to set up six light meters in different positions, all recording light readings every 15-20 minutes. Bowling machines were used to replicate match conditions as far as possible although crucially, because this wasn't a match situation it meant nothing was at stake for the batsmen. They could, as a result, be relied upon to give as objective an account of the light as possible and not - as had historically been the case - use it tactically depending on the situation of the match. Using bowling machines (with no bowler to lock onto visually for a batsman) could, however, potentially affect reaction times.

The Ring of Fire lights at Dubai Stadium were only turned on one of the days. Red balls were used against white sightscreens, but orange, pink and white ones were also trialled for comparative purposes. The key reading was taken from where the batsman stood, looking at the sightscreen.

When play began in sunshine, the lux levels - a measure of the intensity of light - were around 19,000 on both days. There was a sharp drop - partly because of how shadows form in Dubai's stadium - but by 5.35pm, the lux level was down to between 3800-3900 both days. At this time, players felt the light was unfit for fast bowling. Ten minutes later all kinds of bowling had become unsafe (lux level 2750 on the first day and 3270 on the second).

On the second day, the lights were turned on at 5.45pm and within five minutes, the lux level went up to 5510, supplementing the natural light. But it didn't last long. As the natural light continued to fade, by 6.05pm - 20 minutes after the lights had been switched on - conditions were considered borderline: batsmen and fielders were struggling to sight the ball. Five minutes later, conditions were deemed unsafe, lights having bought 20-25 minutes in all.

It became clear that once light levels dipped below 3800 lux, play would have to stop. Floodlights did definitely help but for how long would depend on their quality, and the rate at which natural light deteriorated at that venue. It's important to understand that number wasn't a universal level. In England, for example, the same city could have different findings: the unsafe level at The Oval was found to be lower than at Lord's. Even at the same ground, light conditions could be different at different ends, because of how the grounds were built and the sun set.

Because of this variation, there can't ever be one standard level and why the decision comes down, ultimately, to the judgment of the umpires. The light meters they use don't measure light in lux levels and they only look at a reading after they've made the decision to go off the first time; subsequently they use the meter before making a decision as a benchmark, not as an absolute level of the light.

Back in 2011, the ICC's suggestions were that using a pink ball would allow play to go on longer (switching between different-coloured balls has never been considered a practical solution though); that umpires were still best-placed to make a call on when light is unsafe; and that earlier start times would see finishes before natural light fades. Those were also the suggestions presented the last time there was in-depth discussion on the matter, in 2013.

Nearly a decade on from the trials, they are likely to remain the suggestions when the ICC's cricket committee meet next to discuss it.