NETTCP Roadway Design & Maintenance 5 — Questions and Answers
Question 1: What pavement layer is responsible for distributing wheel loads to reduce stress on the subgrade?
- Surface course
- Tack coat
- Base course (Correct answer)
- Prime coat
Correct answer: Base course
The base course distributes applied wheel loads over a broader area of subgrade, reducing stress concentrations that would cause rutting or subgrade failure.
Question 2: Which New England-specific environmental regulation most commonly affects highway drainage design?
- Clean Air Act Section 309
- Section 404 of the Clean Water Act regulating wetland fill (Correct answer)
- NEPA categorical exclusion thresholds
- Federal Motor Carrier Safety Act provisions
Correct answer: Section 404 of the Clean Water Act regulating wetland fill
Section 404 of the Clean Water Act requires permits for discharge of fill material into wetlands, which are abundant in New England and frequently impacted by highway drainage work.
Question 3: A roadway maintenance crew discovers delamination between an overlay and the existing pavement. What was the MOST likely cause?
- Excessive compaction temperature during paving
- Inadequate or missing tack coat application (Correct answer)
- Too-thick overlay lift placement
- High traffic volume during curing
Correct answer: Inadequate or missing tack coat application
Delamination between pavement layers is most commonly caused by insufficient tack coat, which provides the bond between the new overlay and existing surface.
Question 4: When establishing horizontal alignment in mountainous New England terrain, which design constraint MOST limits the use of sharp curves?
- Environmental noise impacts on wildlife
- Maximum allowable superelevation combined with design speed (Correct answer)
- Pavement marking reflectivity standards
- Right-of-way width for utility relocations
Correct answer: Maximum allowable superelevation combined with design speed
Maximum superelevation rate (typically 8–10% for highway design) combined with design speed sets the minimum curve radius that can safely be used.
Question 5: What is the primary reason highway agencies in New England apply sand or sand-salt mixtures to icy pavements rather than salt alone at very low temperatures?
- Sand provides friction when road salt loses effectiveness below about 15°F (−9°C) (Correct answer)
- Sand melts ice faster than salt in subzero temperatures
- Sand prevents the pavement from cracking due to thermal stress
- Sand is required under state environmental regulations above salt
Correct answer: Sand provides friction when road salt loses effectiveness below about 15°F (−9°C)
Road salt loses significant deicing effectiveness below approximately 15°F, so sand is applied to provide mechanical friction on icy surfaces when salt cannot melt ice.
Question 6: During roadway reconstruction, the specification requires proof rolling of the subgrade. What does this procedure verify?
- That the asphalt has achieved target density
- That the aggregate base course gradation is correct
- That the subgrade is uniformly stable and free of soft spots (Correct answer)
- That the roadway profile matches design grades
Correct answer: That the subgrade is uniformly stable and free of soft spots
Proof rolling passes a heavily loaded vehicle over the subgrade to identify soft, unstable areas that deflect visibly and require undercut and replacement.
Question 7: Which standard governs the minimum retroreflectivity requirements for traffic signs on public roads in the United States?
- AASHTO Green Book
- FHWA Final Rule on Minimum Retroreflectivity (23 CFR Part 655) (Correct answer)
- OSHA 29 CFR 1926 Subpart G
- ITE Traffic Engineering Handbook
Correct answer: FHWA Final Rule on Minimum Retroreflectivity (23 CFR Part 655)
The FHWA Final Rule under 23 CFR Part 655 establishes minimum maintained retroreflectivity levels for traffic signs to ensure nighttime visibility.
NETTCP Roadway Design & Maintenance 5
What pavement layer is responsible for distributing wheel loads to reduce stress on the subgrade?