air traffic control airline airplane airport architecture atc aviation berlin command control control tower flight fly holidays plane radar standby tower tower signal tower views tracking traffic air-traffic-control aircraft architectural communications control-tower directions directives flying height high safety tower-signals tower-views visibilty authorities authority black blue car flashing lights lights motor vehicles police red traffic control vehicles warning warning lights white access armed availability available communicating communication deployment equipment law law-&-order light National-Day naval navy on-duty on-the-job order patrols power presence regulations responsible river river-traffic secure security Singapore traffic-control weapons barrier closed road sign construction detour do not instruction restriction temporary turn badges barriers cars flashing-lights motor-bikes police-vehicles symbols uniforms