Conversation so far:
What did Willie Brown do for mass transit?
One of Brown's central campaign promises was his 100-Day Plan for Muni, in which he boasted he would fix the city's municipal bus system in that many days
Did Willie Brown improve mass transit?
Yes, with the help of voter-approved initiatives
What were some of the mistakes Willie Brown made?
During his first term as mayor, Brown quietly favored the demolition and abolition of the Transbay Terminal to accommodate the redevelopment of the site for market-rate housing

Question: What was the biggest improvement he made?
Self-contained rewrite: What was the biggest improvementWillie Brown made?