The couple of times I have used Queenstown Road or the nearby Battersea Park after dark there were no issues - well lit and trains passing frequently. One thing the undesirables don't like is being watched..... The estates towards the gate into Stewarts Lane are a different matter.
Pokesdown isn't at all nice, too many druggies in the area. On a track renewal job a few years ago, the first job in daylight was to go "needle picking" from the track to be relaid. To save any problems, all signing on and messing facilities were some distance away with security guards on the gates to road and railway. ( 52 hours to relay about 600 yards plus three full sharps containers and some flick knives for disposal!)
The last train out of any major town on a Saturday night can be unnerving. Not drugs, knives or treats of violence, just loads of 20 something women "lubricated" up to the eyeballs. I've heard swearing around the docks, railways and road haulage, but they would make any old docker blush ..... it's a different level and feels threatening.