one of the characters, whilst in a sewer/subway system - perhaps fleeing danger (be it men with guns, something unspeakable twitching beneath Guadalajara International Airport, a giant radio active alligator under the streets of Trieste, whatever) - finds a ladder/shin up, to a manhole opening, which they get open (if being actively pursued then insert a few hairy moments when it appears shut tight), only to realise as they pop their head out topside that the road above is slick with fast-moving vehicular traffic.
facial expressions can be key here.