The speaker imagines a bridge built where no river exists, and treats it as something people sometimes need: a lift off the ground that gives a sweeping view without any effort of climbing. The title suggests the words are meant for drivers stopped at a checkpoint, and that setting colors everything. The sky and water seem to wear "the calm / blue uniform of authority," so the landscape itself looks like a watching officer.
The tone starts almost gentle, offering a pause and a chance to "get in touch with who / we really are." Then it tightens. The cables are "high-strung," the travelers "dry-mouthed or sweaty," and the closing image of death being "as close / as a sudden, wild leap" turns the calm into a charged moment. The mood is uneasy and quietly tense. Being stopped, questioned and looked over, the poem hints, can force a kind of honesty, and it can also bring a dizzy temptation to bolt.