New York as Hellscape
The opening imagery of Taxi Driver situates the viewer in a hellish setting, smoke billowing through the dark streets and red light illuminating Travis's face as he drives through midtown. The perilous and dark imagery turns Manhattan into a hellscape, and foreshadows that dark and disturbing events are likely to take place. Slowly cutting a path through the thick steam rising from the ground is a yellow cab. Travis moves through this landscape as if wandering through the underworld. The lights of the facades in Times Square are stark and often red, and the lights of the brothel where the climactic fight takes place are dim and brownish red, with an abundance of candles burning in Iris's room. The hellish atmosphere leads us to wonder whether Travis is a demon or a redemptive angel.
The Empty Hallway
After their second disastrous date, Travis calls Betsy and delivers a rambling, desperate monologue explaining his behavior and begging in vain for a second chance. As he apologizes into the payphone, realizing that he’s not going to get another chance to make up for his mistake, the camera steadily pans away from Travis and lingers on a long, empty hallway. The imagery of the empty hall symbolizes the loneliness that Travis feels not only at this moment of rejection, but also existentially in his life at large.
The image of an empty hallway recurs as the setting for Travis's violent rescue of Iris. When Travis first enters the brothel, he walks down a long dark hallway towards his task, shooting a man, and getting shot himself in the neck by Sport. Again, the hallway represents Travis's loneliness, but inside the brothel it takes on a second connotation as well: the dark corridor, and the violence that waits for him at the end, are Travis's fate: the inevitable dark end of his self-righteous isolation.
Fizzy Bubbles
A fascinating bit of imagery is the tightly shot image of an Alka-Seltzer tablet bubbling and fizzing in Travis's glass of water. Inside the diner, as Travis sits with his fellow cabbies, the camera takes Travis's perspective as it moves in closer to the bubbling water and the conversation taking place around him is drowned out by the fizzing sound. The fizzing of the water represents Travis in his own self-imposed bubble. His consciousness, like the water, is starting to fizz, drowning out all external stimuli and bubbling over percussively.
Reflections
Travis looks at his own reflection as he practices his quick draw and rehearses an imagined attack against a dangerous assailant. Alone in his apartment, Travis enacts the alienation he feels on a daily basis, and explicates his persistent expectation that he is on the brink of being attacked. Travis does not choose a fake target, but looks at himself in mirror image; he is at once the attacked and the attacker. This becomes a potent image in the film, because it communicates that Travis is unable to distinguish between his external reality and his internal demons. He is simultaneously disappointed and disgusted by the world, and also a complicit offender himself. This splitting of Travis's identity as represented by his confrontation with his mirror image confirms his deteriorating grasp of reality.
The Mohawk
In 1976, the mohawk hairstyle was an incredibly shocking piece of imagery, signaling both an anarchist punk impulse, a traditional Native American hairstyle, and a symbol of the American military in Vietnam. Indeed, Scorsese was inspired to incorporate the hairstyle into the film after talking to a friend who had fought in Vietnam and told him that soldiers often sported the haircut before making a kill.
When Travis's mohawk is revealed at the Palantine rally, the audience sees the extent to which he has excused himself from mainstream society, and explicates his intentions to "go in for the kill."
