Beijing　municipal　highway　administration　started　to　collect　pavement　condition　data　on　its　major　expressways　since　2006.　It　is　advised　in　the　Chinese　practice　standard　that　data　collection　shall　be　conducted　on　annual　basis.　However,　pavement　data　are　usually　collected　at　different　seasons　of　the　year,　which　may　cause　significant　seasonal　variations　in　the　observed　condition.　Moreover,　for　some　reasons,　data　are　missing　for　some　of　the　pavement　sections　at　certain　years,　which　could　bring　up　difficulties　in　performance　model　estimation　and　inference.　These　concerns　have　been　simply　neglected　in　past　practice.　This　study　proposed　an　unevenly　spaced　dynamic　panel　data　model　to　investigate　the　seasonal　patterns　of　a　performance　indicator　called　Ride　Quality　Index　(RQI).　A　quasi-differencing　approach　was　adopted　for　the　estimation.　Data　collected　from　the　5th　Ring　Road　of　Beijing　were　used　in　the　case　study.　It　was　found　that　RQI　data　collected　during　the　fall　season　are　expected　to　be　lower　than　that　collected　during　the　spring　or　summer　seasons.　Findings　from　this　research　would　be　helpful　to　pavement　engineers　in　using　unevenly　spaced　pavement　condition　data　for　future　condition　estimation.