How can the reader respond?
By telephone, via email, via a website, etc.
How can the reader co-operate?
What can they do to be of assistance?
How will the event be carried out?
How do I establish a good relationship with the reader?
In your use of language, take into account that the letter is meant for a large group of people. It has to be understandable to everyone. Keep this in mind when you organise the letter. For example, you could make use of headings. Present the information in a logical order.
Show consideration for your readers. For example, if residents will be inconvenienced by roadworks, point out how the changes will benefit them in the long run. Give the reader the opportunity to ask questions.