Vauxhall ADAM engine overheating in static traffic

When stuck in traffic you dont get any airflow to cool radiator . The engine cooling fan should kick in when it reaches a certain temp. to rectify this . but often on some cars just before it reaches hot . You could check your coolant level first and make sure engine fan is operating o.k , you may hear it operating when driving and it kicks in . If still having problems it may be a faulty sensor or thermostat late in opening .