Hi, welcome to the Forum,
I don't know this subject at all to be honest but have extensively researched as best I can to find:

From an old Auction Catalogue:

"LOT 242, 1784-1871 Ledbury Turnpike Road.
Extensive archive of documents and ephemera relating to the Ledbury Turnpike Road, Herefordshire, comprising tradesmans bills, for raising stone for the road, its repair and maintenance, Bills to Parliament concerning the road, notices to gatekeepers, rates of tolls, balance sheets, letters and notices from and to the Trustees, a map of part of the route, printed Acts of Parliament, printed auction advertisements for the sale of the various goods and chattels of the road in 1871 and many many more, all cont. in a metal trunk One of the most important and comprehensive archives for a turnpike road to be offered in recent years. These unique papers and documents provide the entire history of the road, from its concept in 1784 to 1871 when the toll houses were demolished and the toll gates, posts and rails were sold as this, along with all turnpikes, were overtaken by a national road concept maintained at taxpayers expense rather than by tolls. The Ledbury Turnpike continues to survive as an identifiable route . It is now the A438 from Hereford, through Ledbury to its junction with the present day A38 at Tewkesbury."
http://www.durtnall.org.uk/DEEDS/Herefordshire%201-100.htm

"PARKHOLD, a township, in the parish and union of Ledbury, hundred of Radlow, county of Hereford, 2 miles (S. by E.) from Ledbury; containing 42 inhabitants. It is situated near the western base of the Malvern hills, on the borders of Gloucestershire, and contains 383 acres of a well cultivated soil.
From: 'Park - Parwick', A Topographical Dictionary of England (1848), pp. 535-537. URL: http://www.british-history.ac.uk/report.aspx?compid=51204&strquery=parkhold Date accessed: 12 July 2011.

Using Streetmap etc etc I haven't found Parkhold, does it still exist ?. I've found "Parkway", a large house rather than hamlet, in the abovementioned area "2miles SE of Ledbury"... yet other "hits" suggest its near Trumpet to the West of Ledbury !. Sorry I don't know this area too well...and placenames seem to have changed ?
http://www.aboutbritain.com/maps/ledbury-map.asp

Thes sites may help ?

http://www.hartpuryhistoric.org/milestones.htm
(see various pages including "Turnpikes" marked at top)

http://www.ledburyportal.co.uk/portal/index.php?option=com_content&view=article&...
There are various contact names on this site who may well be worth asking ?

Assuming you know approximately where Parkhold is, this site's maps may show the Turnpike. Its a fantastic site containing various OS Maps of various ages throughout Britain and the maps can be greatly enlarged, just click on the blue map names to LHside to select a map. The uppermost First Series map is beautiful B&W c1831 !
http://www.visionofbritain.org.uk/maps/index.jsp?layer=europe&xMin=3161880.00285&am...

I guess this might be your "ultimate" solution, "Ledbury Turnpike Trust" ?
http://www.nationalarchives.gov.uk/nra/searches/subjectView.asp?ID=O18668&tabType=A...

Hope this helps in some way, Happy Hunting !