The Roman road from Cassel to Pont de Thiennes runs due south to Boeseghem and the bridge over the Lys at Thiennes. Its track has been confirmed by numerous soundings. Communal boundaries follow it for the entire length of its course. There is no trace of the road on the south bank of the river. Probably the road was used to link to a river transport terminal at the point where the Lys became navigable.

The road is marked by a steep footpath as it descends from (presumably) the south gate of the castellum. Oxelaere (Oscularum 1135, Ger. lar = clearing, with oks = ox ) is on the left connected to the road by two lanes obviously later than the road's construction. Soundings have revealed a 7.5 m wide gravel bed edged by slabs of sandstone. On the road from Cassel to the station numerous objects associated with cremations (500 red slip vases, 20 white slip vases and several lamps and statuettes) were found at a depth of six metres in the sand.

Sounding in the 19th century on the line of the road just north of the railway revealed a 7.5 metre wide gravel bed edged by sandstone blocks at a depth of 40 cm.

The stretch of road from the base of the hill of Cassel to Wallon Cappel (Lat. Capella = chapel, with Walloon = Gaulish speakers) crosses an area of small regularly spaced fields possible laid out in Roman times as agricultural estates.

South of Wallon Cappel, on the boundary of the commune of Morbecque with Sercus (Sarcus, lat. sarcophagus = tomb), soundings showed the road to be 6.2 metres wide and composed of 11 cm of packed earth with pebbles. Nearer to Morbeque, in 1993, Gallo-Roman traces of occupation were found.

North of Steenbecque (Ger. Steenbeka + stone stream) east of the road line tiles and potsherds from the La Tene III were found. A section on the Blaringhem (Ger Blatharingas ham = the farm of Blathar's people) boundary showed the road to be 4.4 metres wide and composed of pebbles. The width between its boundary ditches was 9.4 metres.

A sounding on the Boesighem (Ger. Busingahem = Bosingas ham, the farm of the people of Boso) boundary showed the road to be composed of pebbles and 4.8 metres wide. Between boundary ditches it was 11 metres wide.

The crossing of the Lys where the Pont de Thiennes (Ofr. tienne = hill) now stands, marked the boundary between the territory of the Menapi and that of the Morini. At this point the Lys becomes navigable and a river port marked by a small sanctuary seems to have existed here. Three statues in bronze of Roman divinities were found here during the work on the bridge. The river port will have been used to export salt from the working of the Menapi on the coast via the Escaut. Cassel was also known as far away as Rome for its excellent salted hams. There is no trace of the road on the south bank of the Lys.

The road from Cassel