 The story was partially autobiographical for  Paul Schrader (I) (qv), who suffered a nervous breakdown,  literally didnt talk to anyone for months, went to porno theaters  and developed an obsession with guns when he first moved out to Los  Angeles. Schrader decided to switch the action to New York City only  because taxi drivers are far more common there. Schraders script  clicked with both Scorsese and De Niro when they read it.