Merge overlapping lines in ArcGIS

Dissolve Lines

update link (28th October 2014) http://resources.arcgis.com/en/help/main/10.2/index.html#//00170000005n000000 Single Part & DISSOLVE_LINES enable in the geoprocessing tool.

If you use an ArcEditor license you could start ArcCatalog and:

1. make a personal Geodatabase.
2. create a Feature Dataset in the Geodatabase.
3. Import your Shapefile in the Feature Dataset.
4. Create a Topology in the Feature Dataset.
5. Set the Topology Rule "Must not overlap" for your Layer.
6. Run the Topology Validation.
7. Check the results in ArcMap - you need to add the Topology Error Layer.

This will markup all the overlapping lines.

Hope this helps you :-)