The Main Street Bike-Lane Op-Ed and the Missing Denominator
Devon, a hardware-store owner, has written a 600-word op-ed for the Riverbend Gazette (population 38,000) opposing a council proposal to convert 2.1 miles of Main Street from four lanes to two lanes plus a protected bike lane. The council votes in three weeks. Devon's draft ends: "The council's plan will destroy local business." His evidence: (1) a study of cycling corridors in a city of 800,000; (2) a pilot-period figure showing bike injuries on Main Street rose 40 percent after the lane opened; (3) one neighboring shop owner who says her revenue fell 15 percent; (4) an 18-month construction schedule buried in the council packet. He does not mention the city's own count that daily bike traffic on Main Street went from 90 to 310 riders during the pilot. His editor has asked for one revision pass before publication and warned that the Gazette fact-checks every number.
1. Evaluate Devon's four pieces of evidence: which supports his conclusion and which does not, and why? Identify the specific error in his reasoning about the 40 percent injury figure.
Read the worked answer
Ranked by fit to the claim:
- (4) The 18-month construction schedule is the strongest item: local, documented, and directly relevant to a narrow claim about foreseeable disruption to customers and deliveries.
- (3) The single shop owner is a legitimate anecdote, but n=1 supports only "one nearby business reports a decline," not "business will be destroyed." It works best as an illustration attached to a broader claim.
- (2) The 40 percent injury rise is the weakest sort of number - a change in a raw count with no denominator.
- (1) The 800,000-city study has an external-validity problem: a corridor in a dense metropolis does not transfer automatically to a 2.1-mile stretch of a 38,000-person town. It can support "cities that tried this saw X," not "Riverbend will see X."
The error in the injury figure: base-rate neglect. Riders went from 90 to 310 daily, so exposure roughly tripled. If injuries rose 40 percent while ridership rose 244 percent, the per-rider risk fell sharply. Devon is comparing a count to a rate. Because the Gazette fact-checks numbers, he should request injuries per rider (or per rider-mile) before publication - publishing the 40 percent without the rider count invites a correction and destroys his credibility on the numbers that do hold.
2. Rewrite Devon's final sentence so it is arguable, scoped to what his evidence can support, and still forceful. Explain each change.
Read the worked answer
Original: "The council's plan will destroy local business."
Three defects: "destroy" is an absolute that no evidence could establish in advance; "will" asserts a certainty about the future; and "local business" is unbounded, so a single counterexample refutes it.
Revision: "Converting Main Street to two lanes would put eighteen months of construction in front of shops that already run on thin margins, and the council has not published a plan for keeping customers able to reach them."
What each change buys:
- "Destroy" becomes a mechanism - construction duration plus access loss - which is something a reader can evaluate and a council can answer.
- "Will" becomes "would," a conditional appropriate to a proposal not yet adopted.
- "Local business" narrows to businesses facing the specific disruption, which a single surviving shop cannot refute.
- The final clause converts the claim into a checkable assertion: the council either has an access plan or it does not. If it produces one, Devon's argument narrows honestly; if it cannot, his case is stronger than the original hyperbole ever made it.
3. Devon must add a counterargument with a response. Draft the two or three sentences he should add, using the 90-to-310 rider count, and explain why conceding a fact he omitted strengthens rather than weakens his case.
Read the worked answer
Suggested sentences: "Supporters are right that the lane is being used: daily bike counts on Main Street rose from 90 to 310 during the pilot, and a lane nobody rides would be a failure. But that growth is precisely why the injury figure needs a per-rider denominator, and it is why the real question before the vote is the eighteen months of construction - not whether cyclists exist."
Why concession strengthens the argument: the editor and the council already know the ridership number, and an opponent will supply it within a day of publication. A writer who concedes it first controls where it sits in the argument and what it is allowed to prove. Suppressing it creates a single point of failure: the reader who notices the omission stops trusting everything else, including the construction schedule that is Devon's genuine case.
Conceding also forces a better structure. Once ridership is granted, the argument cannot rest on "nobody uses it" and must rest on cost, access, and transition - the claims his strongest evidence actually supports. That is the difference between winning a fact-check and winning a vote.