function displayMarkers(group) {
    
    setControlActive('tripsControl',       group == 0);
    setControlActive('tripTimesControl',   group == 1);
    setControlActive('bothMarkersControl', group == 2);
    
    setGroupActive(trips, group == 0)
    setGroupActive(tripTimes, group >= 1)
    setGroupActive(tripsSmall, group == 2)
}

function setGroupActive(group, active) {
    if(group.active != active) {
        if(active)
            group.activate()
        else
            group.deactivate()
    }
}

function setControlActive(controlName, active) {
    control = document.getElementById(controlName)
    control.className = active ? 'marker-control-active' : 'marker-control-inactive'
}