show the positioning

I'm not sure that I understand what you mean with 'create a new road'. Do you mean a physical road, or did you add it to OSM ? In the latter case you could use the "Share" button on openstreetmap.org and send the link to your client. That link will show the road on OSM.

Of course this will never help you client if she/he uses navigation software that is not based on OpenStreetMap. Even with navigation software based on OpenStreetMap it will depend on when your client updates the maps his/her software is using.

If you can to browse the exact point where you leave the road you could send the ULR which contains the co ords in it like this http://www.openstreetmap.org/#map=16/51.7268/-1.9324 you could also send the campsite location like this http://www.openstreetmap.org/#map=16/51.7311/-1.9300 Satnavs do have the option to enter lat longs if there isn't a postcode or address. Using the share button on the slippy map allows you to add a marker to the map. If you record your new road as a GPX with a satnav or a gps you can upload the trace to OSM ready for mapping. If you can map it from the licensed aerial that is available as a background in iD Potlatch2 or JOSM editors it can be mapped from local knowledge quite quickly. If the route from the road is long and confusing you could, if you don't have time to map new road then send them a series for co ords to follow ( known as a route) assuming they can use them in their satnav or gps.

You can send the link to the people through OSM.