A friend runs a charity (no names - no pack-drill) which has a number of sites around the countryside which are open 24/7 for visitors. The sites have all got a traffic monitoring system that clicks over every time a car comes in through the entrance, and I have just helped him download this data from a reader onto his PC so that it can be used to measure visitor levels. The data is just the time and date of the arrival of the visiting car. No big deal here until we start looking at the data: this shows a fairly steady string of visitors, with seasonal and weather variations, during daylight hours which is what you might expect. What we did not expect was the high peak of visitors between 0030hrs and 0300 hrs. Given this is a countryside place with almost all the benefits being visible during daylight, what do you suppose is going on?
Answers on a postcard please!

False positives from animals maybe? I don't know if this applies to the English countryside though.

arboretum?

Kids having "backseat adventures" in the "empty" parking lot?

LOL B00kWyrm, my other guess was 'submarine races'

It won't be animals as only car sized lumps of metal set the detector off 1 count. Bicycles don't count but big bikes do.
Submarines would count but we are miles from the nearest water - or perhaps you could explain that reference!!

When I was in college, we often referred to having "backseat adventures"
as "parking"... "making out"... or "going to watch the submarine races".
Of course, that college was on Point Loma, in San Diego...
so we really could watch the submarines... on a bright night.

And there I was thinking it was a naughty game for the back seat!

lol, sure,
back in the day 'going to watch the submarine races' was a euphemism for just what B00kWyrm said
parking down by the river and having a go in the backseat with your sweetheart...or somebody's sweetheart.

Usually better with somebody else's sweetheart as this often added to the general excitement....

Maybe they park on top of the sensor and you are counting the "bounces"

ah yes...i remember..."if the vans a rockin dont...... like some version of a pedometer...i wonder what you would call that device?

Is there an abundance of empty beer cans/bottles, needles, or other trash? or any damaged property? If so then I'd see about getting the local authorities to go out there around that time. If not, then it may just be kids having some fun, but that seems a bit late, I'd just figure at that time they'd be better off doing that at home with parents asleep.

Back in high school there was a parking lot for some businesses and a bunch of kids would gather there, eventually people complained (presumably about trash) and kids were allowed to stay there anymore. So they moved to a doctor's office parking lot, that worked fine until some ***** left a bunch of empty beer cans in the parking lot before driving off, now there are gates that get shut when the office isn't open.

I award you the prize for the most outrageous explanation!

Maybe its the police department giving extra attention / looking for potential trouble?

Back in the day...
I worked security for that same school mentioned above...
and we (security guards) were active around those hours,
both in vehicle and on foot, looking for potential trouble spots.

That's the time slot that most misdemeanors took place too.