Construction, Maintenance of Traffic, and Preservation
Work zones (MUTCD Part 6)
A temporary traffic control zone has four components: advance warning, transition, activity area (with buffer space), and termination. Merging taper length is L = W × S for speeds of 40 mph or less, and L = W × S²/60 for 45 mph and above, where W is the offset width in feet and S the posted or operating speed. Buffer space protects workers and must never be used to store equipment.
Maintenance and preservation
Treatments range from crack sealing and chip seals through microsurfacing and thin overlays to mill-and-overlay and full-depth reclamation. Preservation extends service life when the pavement is still structurally sound; it is not a repair for structural failure. Joint and crack sealing keeps water out of base layers.
Quality and acceptance
QC/QA specifications use contractor testing and agency verification, with percent-within-limits (PWL) translated into pay factors. Density, smoothness (IRI), and thickness are common acceptance items; failing lots may be accepted at reduced pay or removed.
Traps
- Using the ≤40 mph taper formula on a 55 mph facility.
- Omitting buffer space or placing it before the transition.
- Applying a preservation treatment to a pavement with structural distress.
- Treating PWL as an average rather than a measure of variability.
Worked example
A 12-ft lane is closed on a 55 mph highway. Since 55 ≥ 45, L = W × S²/60 = 12 × 55²/60 = 12 × 3,025/60 = 605 ft of merging taper, plus buffer space before the work area.