Here’s how you can fill in the missing transitional words in the paragraph:
The city is proposing a long-overdue bike-helmet law that would make wearing a helmet mandatory for all cyclists. This law will help protect cyclists of all ages from potential injury. Many studies have shown that wearing a bike helmet can prevent serious injury and death. For example, a study in 2009 showed that 91% of people who died in bike injuries were not wearing helmets. In another example, a similar study in New York found that 74% of bike crashes involved a head injury, and almost all cyclists who died, 97%, were not wearing a helmet. However, some people claim that wearing a bike helmet is uncomfortable. Yet new helmets are lightweight and designed with air vents so you will not overheat while wearing one. In conclusion, a bike-helmet law would help make biking safer and, by extension, more enjoyable.