Given the following passage  "Pockets of Georgian architecture survived the war, but much of the city was levelled. There has been extensive redevelopment since World War II. Increasing traffic congestion in the 1920s led to partial demolition of medieval walls around the Bargate in 1932 and 1938. However a large portion of those walls remain.",  answer the following question. Note that the answer is present within the text.  Question: Why were there still walls remaining?
Answer:
partial demolition