There actually is an option; it is the "Block Route" feature in the menu; it will ask if you want to block .5 miles in front of you, 1 full mile in front of you, etc. It's a really rocky and odd way to do detours as I am used to Garmin having the simple "detour" button to do a different route, but it doesn't work; e.g. if you select "1 mile" as what you want marked as blocked, it will block 1 mile of road ahead on the current route and then reroute you. However, if you know 5 miles down the road that there is a block, you can't block that as you can only block what is right in front of you for so many miles. It's a really odd feature and they set it up very awkwardly, but it's there and it works.