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Location Map ( geo)
Cameraicon.png View gallery (11)
From:  Probus (SW897466)
To:  St Mawes (SW841327)
Via:  Tregony, St Just in Roseland
Distance:  15.3 miles (24.6 km)
Meets:  A390, B3287, B3289, A3078
Former Number(s):  B3288, B3287
Old route now:  A390
Highway Authorities


Traditional Counties


Route outline (key)
A3078 Tresillian – Probus
A3078 Probus – St Mawes
This article is about the current A3078 from Probus to St Mawes.
For the former A3078 in Plymouth, see A3078 (Plymouth)
Percuil River crossing


The A3078 is a mostly winding rural route on the Roseland Peninsula in Cornwall.

It starts by turning south off the primary A390 on the Probus bypass. Initially passing fields, the road drops slightly to enter woodland and cross a stream and valley, which it then follows through the trees for a while. Turning away from the stream and emerging from the tress, further farmland is passed.

The road drops again towards the Fall River at Tregony. Despite being 15 miles from the sea via river, it was navigable to this point and Tregony had a port and was considered a town. The river silted up and Penryn and then latterly Falmouth became the river's main ports. Crossing the Tregony Bridge, there is immediately a turn on the left for the B3287 which leads to the village proper and eventually back to the A390 nearer St Austell.

Climbing away from the river the bends and the rural outlook continue. At Bessybeneath, which is no more than a couple of houses, is a turn for Veryan and also a garage. Fuel stops on the Roseland Peninsula are very limited and it may well be advisable to stop here if you are running low. The former garage a few hundred yards away on the other side of the road has been long closed.

The next section is straighter and an overtake or two may just be possible. The road reaches Ruan High Lanes which is not much more than a hamlet but it does have a 40 mph limit. After that it's more of the same to the next hamlet, Trewithian, which also has a 40 mph limit.

Significant bends lie ahead and in this section is a narrow part where there is no centre line for a short while. At Trethem Mill is another 40 mph limit and the road passes the head of the tidal Percuil river. It climbs Mill Hill to reach St Just In Roseland, which has a 30 mph limit; the road is very narrow in the village. There is a turn on the right here for the B3289 heading to the King Harry Ferry. Just past that turn is a single-track lane leading to St Just In Roseland Church. It is worth a detour here as the churchyard, set in a subtropical garden right next to St Just Creek, is widely regarded as one of the most picturesque in Britain.

Rising away from the village, the 40 mph limit is resumed and shortly thereafter a good view on the right appears over Carrick Roads, a very wide, flooded river valley.

The road reaches a fork and both ways are numbered A3078. The one on the right has weight and width restrictions, so continuing on the left branch (which is the mainline anyway), we drop down to St Mawes and a 30 mph limit. In front is another flooded valley and the Percuil River again. The road turns right and reaches the coast to pass directly along the back of the beach to the harbour area. In several sections along here the road is extremely narrow, not much more than one car width. This is perhaps the A road with the narrowest point in the whole country.

The road climbs a 16% hill to reach St Mawes Castle, where the Percuil River joins Carrick Roads just before flowing into the sea and there is a fantastic vista. The road then turns inland round a very tight bend and continues to rise. Back to a 40 mph limit, it passes the mostly bungalow suburbs of St Mawes before it shortly reaches and terminates itself at the fork junction previously mentioned.


The road was shortened at its top end on the opening of the A390 Probus bypass. It used to end at what is now the junction of the A390 and the B3275 (formerly the A39) near Tresillian. The second half of the bypass followed the route of this section of the A3078 with widening, improvements and straightening of the curves.

On first numbering the whole of the route south of Tregony was part of the B3287 and the route north of Tregony was the B3288. This was changed in the 1935 re-renumbering when the A3078 was allocated to this road. The route was also changed somewhat, north of Tregony, at that time. It previously went up a steep hill along the straight road northwest of the village but was diverted to a more circuitous route that followed the contours.

Related Pictures
View gallery (11)
Trewithian - Geograph - 478631.jpgA3078 at St Mawes - Coppermine - 7093.JPGA 3078 at St Mawes - Coppermine - 7094.JPGA3078 winding through the woods near Freewater - Geograph - 412784.jpgThe A3078 crossing Percuil River at Trethem Mill - Geograph - 811789.jpg
A3000 • A3001 • A3002 • A3003 • A3004 • A3005 • A3006 • A3007 • A3008 • A3009 • A3010 • A3011 • A3012 • A3013 • A3014 • A3015 • A3016 • A3017 • A3018 • A3019
A3020 • A3021 • A3022 • A3023 • A3024 • A3025 • A3026 • A3027 • A3028 • A3029 • A3030 • A3031 • A3032 • A3033 • A3034 • A3035 • A3036 • A3037 • A3038 • A3039
A3040 • A3041 • A3042 • A3043 • A3044 • A3045 • A3046 • A3047 • A3048 • A3049 • A3050 • A3051 • A3052 • A3053 • A3054 • A3055 • A3056 • A3057 • A3058 • A3059
A3060 • A3061 • A3062 • A3063 • A3064 • A3065 • A3066 • A3067 • A3068 • A3069 • A3070 • A3071 • A3072 • A3073 • A3074 • A3075 • A3076 • A3077 • A3078 • A3079
A3080 • A3081 • A3082 • A3083 • A3084 • A3085 • A3086 • A3087 • A3088 • A3089 • A3090 • A3091 • A3092 • A3093 • A3094 • A3095 • A3096 • A3097 • A3098 • A3099
Earlier routings:
A3010 • A3013 • A3015 • A3017 • A3018 • A3022 • A3023 • A3024 • A3027(E) • A3027(W) • A3029 • A3030 • A3031(N) • A3031(S) • A3032 • A3033 • A3034 • A3035 • A3036 • A3038
A3039 • A3040 • A3044 • A3045 • A3046 • A3047 • A3049(E) • A3049(W) • A3052 • A3056 • A3060 • A3062 • A3063(E) • A3063(W) • A3064 • A3065 • A3071 • A3073 • A3078 • A3079
A3084(W) • A3084(E) • A3087

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