With the help of google map plugin you can display route tab in your map. To add route tab in map , please do with following steps:

Step 1Go to Add or Edit Map page and scroll down to ‘Tabs Settings’ section.
Step 2Enable ‘Display Route Tab’ box as below.

Route Tab
Step 3 Then scroll down to ‘Route Direction Settings’ section and select route directions.
Route Direction
Step 4Save map and open it in browser.

You’ll see the following routes tab on the map.

Display Route tab

Video Tutorial