The salient bits of the stop zone stuff

stopzone.fragment.lua

function removeStopZone(heap,player)
    if heap.stopZones[player] then
        local zone = heap.stopZones[player]
        local success = RemoveSpeedZone(zone.id)
        if success then
            log('Speed zone',zone.id,'removed')
        else
            log('Failed to remove speed zone',zone.id)
        end

        if DoesBlipExist(zone.centerBlip) then
            RemoveBlip(zone.centerBlip)
        else
            log('Failed to remove centerBlip',zone.centerBlip)
        end
        if DoesBlipExist(zone.rangeBlip) then
            RemoveBlip(zone.rangeBlip)
        else
            log('Failed to remove rangeBlip',zone.rangeBlip)
        end
        heap.stopZones[player] = nil
    end
end

function createStopZone(heap,player,place,size,speed)
    removeStopZone(heap,player)
    local location
    local found, Z = GetGroundZFor_3dCoord(place.x,place.y,place.z,true)
    if found then
        location = vector3(place.x,place.y,Z)
    else
        location = vector3(place.x,place.y,place.z)
    end

    local zone = AddSpeedZoneForCoord(location,size,speed,false)
    local center,range = blipLocation(location,size)
    log('Stop zone',zone,'created with blips',center,range)
    heap.stopZones[player] = {
        id = zone,
        centerBlip = center,
        rangeBlip = range,
        location = location,
        speed = speed,
        size = size,
    }
end