We have a 2-1/2 yr old rough collie and a 10 mo old Old English.  The collie is well trained and usually obedient, but barks at activity - whether inside or out, and chases anyone playing, running, riding (especially motorized vehicles) or walking in our yard or on the road.  The OE is still a puppy and is not nearly the barker the RC is, except when outside. One problem is the collie's barking (it's a very loud and intimidating bark, especially since he's a large collie) and sometimes low growl (very often meant as "pet me"). The low growl when being touched by someone is indiscernable from his growl meaning he wants you to pet him and i'm not sure they have different meanings. 

Secondly, we try to let the two of them free in the yard while we are outside also (we have 2 acres) whenever possible for exercise (the Old English needs alot of running around), and try to keep them leashed when we anticipate activity.  However, there are times when they are unleashed and they see someone walking around the court, riding bikes, walking other dogs, delivering packages, etc. and they take off barking and charging whoever happens to be coming.  While I know they are harmless, they are big dogs running at kids and neighbors, barking and would scare anyone.  When I whistle, the Collie will usually stop in his tracks (usually/not always), while the OE will sometimes follow the collies lead, sometimes not.  WHILE WE HAVE TAKEN GREAT PAINS TO MAKE SURE THEY CANNOT RUN AT PEOPLE, IT OCCASSIONALLY HAPPENS.  Neither are aggressive dogs, (the OE hides under a table when too many people come over) - IS THIS BEHAVIOUR NORMAL OR SHOULD WE BE CONCERNED ABOUT THEM HURTING SOMEONE? and WHAT CAN BE DONE TO STOP THIS NEGATIVE BEHAVIOUR? (Our neighbor will not longer let her daughter over because they think the dogs are possible attackers - even though the girl is unphased by them at all - and has been around them since we got both).  Sorry this is so long winded, but needed to set the stage.

I have Beardies which bark and are triggered by movement but in my opinion you have got to get it controlled asap. I've just got a 6 month old rehomed Beardie boy and although he is only a pup I am still working on the jumping up at people. He hasn't been off the lead yet as I've only had him a week, yes I know about Christmas pups but he needed a home.

I don't know if you are in the UK but if you are the dog only has to cause fear in a person for you to be in trouble so I would be getting on top of this habit quickly. I would work on the dogs individually at first as two is a pack and they will take cues from each other. Maybe try a long line so you have control and can reward the behaviour you want i.e. ignoring things/people and can at least control the behaviour while you sort it out.
                                                                         Anne