Sentence:  Before sending me out alone, the company assigned me two "ride-alongs" with its top driver, the legendary Marco, who went out with 280 packages the second day I <WSD>rode shotgun</WSD> with him, took his full lunch break, did not roll through a single stop sign, and was finished by sundown. 
Meaning of the word marked with <WSD> tags:  To ride in the front passenger seat of a vehicle, next to the driver.