So, the dumbasses at my local Department of Transportation decided that it would be a GREAT idea to close one of two lanes of a major freeway at the beginning of rush hour so some guy could walk around taking pictures. Traffic was stopped for 4 miles and getting deeper. This is the second time this week!
It could have been an accident or incident that resulted in a death. They may have been collecting evidence. There are even some police in my area that uses conventional land surveying equipment and rapid high density laser scanners. Precise measurements of things like skids marks and other evidence of how the vehicles came to rest can be used to estimate initial speeds and confirm or refute the testimony of witnesses.
It could also be something more mundane like an actual land surveyor collecting data to support future design work or verify completed projects.
Neither of these are jobs that can be done at night or at times more convenient for your car.