|Location Map ( geo)|
|Distance:||4.6 miles (7.4 km)|
|Met (1923):||A379, A377, A35, A30, A38|
|Now part of:||A379|
|Route outline (key)|
The original A378 was an impromptu Exeter eastern bypass.
The road started on the A379 at Cotfield. It then ran northeast over the Countess Wear Bridge to the A35 just west of the River Clyst. After briefly multiplexing with the A35, it then ran north to Sowton, crossing the A30, and ending on the A38 at Pinhoe.
In 1935, the opening of the Exeter Bypass caused the route to be completely renumbered. The initial section from Cotfield to just north of Countess Wear was upgraded to the A38, the section from here to the B3181 was completely declassified, and the remainder renumbered as a northward extension of the B3181. However, by the 1950s, the central section had been upgraded to the B3182.
The arrival of the M5 downgraded the route even further. Today, the original line of the A378 is the A379 to just south of its junction with the A3015, and unclassified onwards from there. However, part of the downgraded route does still form an important local route through Sowton Industrial Estate.