Air carrier First Officer departing a non-towered airport reported they overflew a vehicle on the runway.

Narrative

Obtained clearance out of ZZZ parked in the run up pad for RW XX. ATC tried to amend our route to go off of DP (Departure Procedure). Asked for clarification and center cleared us to our originally filed ZZZZZ.ZZZZZ1 plan and gave us a clearance void time of less than two minutes. Made a radio call at the departure end of XX stating that we were departing. As we approached V1 both pilots noticed a vehicle in the distance. The PF rotated and we cleared the vehicle by about 150 feet. On climb out; vehicle was queried on CTAF asking for why they hadn't made any radio calls. They stated they had and didn't even realize we'd just overflown them as they were facing north and couldn't see us until we told them.Cause: The slope of the runway being highest in the center was the major cause of this incident. It prevented us from seeing what was happening at the opposite end of the runway and potentially blocked out VHF radio calls from being heard or received. Listening to CTAF on com2 may have prevented us from hearing the radio calls. I believe my departing radio call was on COM1 and they still didn't hear us so that may not have been the main factor. The shorter clearance void time also likely played a roll as we had minimal time to notice the sweeper while performing our before takeoff duties. Suggestions: A control tower at ZZZ would have prevented this event entirely. Due to the airport's geography and busy nature safety margins are reduced and ATC in control would mitigate all of that. Additionally; while I think a clearance void time of two minutes is generally acceptable I might not accept one at an environment as saturated as ZZZ in the future.