for images you should use <%= image_tag('vehiclesButton.jpg') %> if your image is in images directory and it will automagically match the url where ever you are in your app. If you use something like <img src='someimage.jpg'> then it will have some path related problem at some point of time.
if you want to make your image a link then you can either use link_to image helper or simply <%= link_to(image_tag('vehiclesButton.jpg'), :controller => :controller_name, :action => :action_name) %>
hope this helps