PURPOSES : This study evaluates the long-term performance of the asphalt overlay designed by the Seoul pavement design method which determines overlay thickness by considering existing pavement conditions, traffic volume, and bearing capacity of the pavement.
METHODS : A total of 76 sections including 17 control sections and 59 design sections were constructed under various traffic conditions, overlay thicknesses and asphalt mixtures. The performance of the pavements has been monitored up to 60 months in terms of surface distresses, rutting, and longitudinal roughness. The service life of the pavements was estimated to be the period when the Seoul pavement condition index (SPI) becomes 6.0, i.e., a rehabilitation level.
RESULTS : Overall, the service life of the pavements was 72 months in the control and 120 months for the design sections. For relatively thinner overlay sections than designed, the service life reduced significantly; 36 months for 15cm thick overlay and 120 months for 25cm thick overlay. The service life of the pavement in the bus-only lane was 78 months, which is 30 months shorter than that in mixed-traffic lanes. Out of the bus-only lanes, 56% of the pavement along bus stop was deteriorated early to be a poor condition while only 2% of the pavement in a driving lane was degraded to be poor. The overlay with Stone Mastic Asphalt (SMA) in the wearing surface had 38% longer life than that with conventional dense graded mixtures.
CONCLUSIONS : Most of the overlays sections designed by the Seoul pavement design method were expected to survive 10 years, except for bus-only lanes. The control sections having 5 to 10 cm thick overlays showed significant lower performance than the design sections. Thus proper thickness and materials considering the characteristics of existing pavement and traffic volumes should be applied to secure the service life of overlays.

ABSTRACT
1. 서론
2. 서울형 도로포장 설계법
    2.1. 개요
    2.2. 설계 입력변수
3. 추적조사
4. 공용성 평가
    4.1. 설계 및 시공두께에 따른 공용성 분석
    4.2. 도로 구분에 따른 공용성 분석
    4.3. 포장재료 구분에 따른 공용성 분석
5. 결론
REFERENCES

• 박희영((주)로드코리아 기술연구소 책임연구원) | Park Hee-Young
• 이정훈((주)로드코리아 기술연구소 소장) | Lee Jung-Hun Corresponding author
• 김현석((주)한국건설품질시험연구원 부장) | Kim Hyun-Seok
• 김태우(서울특별시 안전총괄실 도로관리과 주무관) | Kim Tae-Woo
• 백종은(서울특별시 안전총괄실 도로관리과 팀장) | Baek Jong-Eun