Wanyai was 125 km from the starting-point at Nong Pladuk. The route skirted a high precipitous cliffon the river bank, then moved on to a hilly zone. Then for roughly 25 km it carried on to the north-west and reached a grassy plain surrounded by thick jungle. There were no trees or shrubs on it and a marvellous hot spring made it swampy. The plain was about 100 metres up from the river level, and a station was being planned here, at Tampii. From the site of the proposed station down to the riverbank the section of track was on a down gradient and had to cross a ravine 30 metres deep.

When I returned to Wanyai in March the CO asked for a study of the route alongside the river. I investigated the point I have just described and worked out that a bridge would have to be 100 metres across, maximum of bridge-piers over 30 metres with 4-metre spans on a wooden bridge, clearly an unstable construction which would oscillate under the weight of a train. I explained to the CO how dangerous this type of bridge design would be and ventured to suggest to him a modification of the route.

One day in late March Daihonéi sent a staff officer to the base at Wanyai to see how the construction was going on. The CO mentioned to him the problem of the bridge and next day we took him as far as the point where the problem lay. Down from the cliff-top the river surface could be seen glittering like silver. In the vicinity dazzling sunlight poured down, the greens of the trees and shrubs took one's breath away, and from the jungle at one's feet the heat seemed to be boiling up.

Mōri, the Survey Unit commander, came out to meet us, pointed out the bridge-building site and explained the problem. It was a precipitous place and both on the map and on the ground a difficult spot to build a bridge. The staff officer was appalled at this topography and turned to Colonel Imai, saying, ‘Regimental commander, why not try a switch-back?’*