The problem is the browser location and navigation bars often get in the way, especially when expanding or shrinking the map display. The SigAlert app solves that issue by presenting a full-screen browser with no navigation bars.
As a bonus, SigAlert also provides a convenient button to "Call Home" so you can let your family know you are stuck in traffic! You can configure the number to dial in the standard iPhone settings menu.
NOTE: SigAlert is not associated with sigalert.com in any way.