PURPOSES: The performance of both string line and multi-sonic sensor systems were investigated with respect to achieving smoothness in a 5 cm-thick Stone Mastic Asphalt (SMA) wearing layer.
METHODS: String line and multi-sonic sensor systems were applied in the leading and trailing lanes, respectively, with two-lane simultaneous paving.
RESULTS: Two systems did not show any significant statistical difference in initial International Roughness Index(IRI). The multi-sonic sensor system produced smoothness similar to that by the string line system.
CONCLUSIONS : The string line system was found to be very effective in eliminating roughness below a wavelength of about 2 m, confirming that a string line reference is the best system to obtain a smoother surface. A multi-sonic sensor system evidently demonstrated the capability of replicating a reference level and, partly showed a roughness averaging effect within the system length. It can further be concluded that the effect of smoothness of the underlying layer on the upper layer smoothness cannot be ignored.

ABSTRACT
 1. INTRODUCTION
 2. PAVER SENSOR FOR PAVEMENTSMOOTHNESS
 3. PAVER SENSOR SYSTEM TYPES
  3.1. Stringline System
  3.2. GPS System
  3.3. Multi-Sonic Sensor System
  3.4. Contact Long-Ski System
 4. METHOD
  4.1. Paving Information
  4.2. Continuous Paving
  4.3. Implemented Sensor Systems
  4.4. Data Collection and Analysis Tool
 5. RESULTS
  5.1. IRI Achievement
  5.2. Effect of the Underlying Layer on the IRI
  5.3. Spectral Analysis for Longitudinal Profiles
  5.4. Direct Profile Comparison
 6. FINDINGS AND CONCLUSIONS
 REFERENCES

• Bae Abraham(Member·Infra ENG Team, Samsung C&T) | 배석일 Corresponding Author
• Lee Hae Sung(Infra ENG Team, Samsung C&T) | 이해성
• Jung Dae Jin(Infra ENG Team, Samsung C&T·Project) | 정대진