If a tree falls down in Sheffield in the middle of the night, does it make a sound?
Well, yes, of course it does. But whose job is it to clear up the mess?
That role goes to the members of the incident support unit at the city's Streets Ahead team. Known as ISU, the group are on call to respond to any urgent job on Sheffield's many miles of highways.
That could be a fallen tree during a storm or a car crash. It could be the discovery of needles on a pathway, or a large pothole that needs to be fenced off. The teams have no idea what to expect when they start their shifts.
"We do anything else that no-one wants to do," joked Darren Goodson, who has worked with the council for 14 years.
"A lot of it is out of hours. A lot of things that come in as urgent.
"You don’t know what’s going to be there before you get to the site. Maybe the call comes from the general public. They report it and we get the job.
"Of a night and at the weekend we do have planned work. There’s a list of jobs that can’t get done in the day. But we do have to drop that if something comes in."
Darren and his colleague Chris Coldwell were speaking from Streets Ahead's Olive Grove depot in Heeley, the day after Storm Aileen hit the city.
Winds of over 60mph uprooted dozens of trees, which all had to be made safe and removed. Darren had just returned from Prince of Wales Road in Manor, where a tree had lost a large branch.
His team was first on the scene, securing the area and closing part of the road until the arboricultural workers were able to get rid of the branch and make the tree safe.
That was a fairly straightforward job, although the need for a quick response is clear.
Some call-outs can be less pleasant. Part of the team's job is to remove dead animals from the highway.
"You are quite lucky if you get to a dead animal before anyone has got to it first," said Chris, a veteran with 38 years of experience.
"When you first get the job you get told it won’t be anything bigger than a dog. But we’ve had a big deer. That’s heavy."
Often the animal is someone's pet. It's a tough part of the job, but the team has a microchip scanner at the depot and usually manages to find the owner to allow for a burial.
Call-outs can also be quite risky. If a report of needles or syringes on the highway comes in, the ISU team is first on the scene.
Park Square roundabout, Hanover Way and the Wicker are particular hotspots, according to Darren, and the teams have to be careful.
"Generally we know whether we are going to be safe to walk into a certain area," he said.
"If it’s in long grass we are not going to go near it. We can only go when we can see where we are stepping. We have specialised teams dealing with large amounts. We barrier it off.
"There have been times where it’s off the highway but if it’s just the one or two, we don’t mind going over to look if we can deal with it.
"You wouldn’t want your own kids round that."
Both Darren and Chris speak highly of their roles and the enjoyment they get. But the job of an ISU worker can occasionally be traumatic.
Teams are called to deal with the aftermath of road accidents, which can sometimes mean clearing what paramedics have left behind.
"I remember a lorry driver got killed," said Chris. "The clean-up was difficult.
"It’s not nice when you see that. It sticks with you.
"But you just deal with things as they come."
Darren added: "You don’t know what to expect when the job starts, but you soon get a feel for the kind of jobs you have to deal with. I don’t really start a shift worrying about it.
"I personally enjoy my job. You don’t know what you are going to get. Sometimes you do a lot and it’s tough, but I think everyone feels that."
The 25-year Streets Ahead contract is reaching the end of the initial five year 'core investment period'. The council aims to have most roads and pavements resurfaced by the end of the year.
Darren admits it has taken 'some getting going'.
But he added: "Recently it seems to have been going a lot quicker. You do see a lot more roads that have been done."