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D. The Antivehicular Sector

20. The overall Communist roadnet in Laos consists of some 650 miles of
 routes extending from Mu Gia Pass to the tri-border area of Cambodia, Laos,
 and South Vietnam. During the dry season, some 400 to 600 trucks are employed
 on this roadnet. Therefore, the number of trucks passing a given point
 during a 24-hour period is very low, and most movements take place during
 hours of darkness.

21. The new elements for the Communists to cope with along the roadnet
 would be the mines and the intensive use of sensors to detect truck movements.
 The system would still rely on air strikes to destroy the trucks, and the Communist
 response would probably be to strengthen existing air defense measures
 and conduct extensive mine clearing operations. This would probably involve
 increased requirements in the daily tonnage of supplies, particularly ammunition
 and food, and in manpower.

22. The road system already included bypasses, truck parks, turnouts, concealed
 hideaways and overhead trellises to hinder air detection. These would
 almost certainly be increased. The Communists would continue to rely on the
 movement of small convoys at night or during bad weather, with considerable
 space between vehicles. Since it is difficult to create new routes for truck
 traffic, and because the sensors would be more effective in detecting the truck
 movements than personnel movements, the Communists would probably devote a
 considerable effort to thwarting the sensors along the truck routes than along
 the trail system. Should these countermeasures be ineffective or too costly,
 the Communists would be forced to attempt to extend the roadnet further west
 in Laos or resort to other means.

E. Alternative Routes and Sources of Supply

23. River Traffic in Laos. Within Laos itself, one alternative for the Communists
 would be increased use of river traffic, but although this is more feasible
 for moving supplies than personnel, it has definite limitations. The only river
 that might be used through parts of the antivehicular sector is the Se Bang
 Hieng which flows west and south from the western DMZ. At present, the
 only access to the river from North Vietnam, however, is via the trail network
 in Laos, but North Vietnamese Routes 102 and 103 could probably be extended
 to the river.

24. Sea Routes. We believe that infiltration by sea has been greatly reduced
 since the beginning of the Market Time Operation early in 1965. Nevertheless,
 if the Communists were willing to risk substantial losses, they would probably
 be able to infiltrate some weapons and ammunition by sea. The use of sea
 routes would be uncertain, and considering the present disposition of Communist
 forces in South Vietnam, it would present them with new problems in the
 distribution and delivery of materials, particularly ammunition. We believe that,
 while the Communists would attempt to increase the use of sea routes as the

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