Developing a proper speed limit for freeway is critical for roadway safety. Due to the difference in visibility between day and night, it is necessary to have different speed limits for the two time periods on freeways with changing geometric features. Aiming to reduce the number of crashes caused by speeding at night on freeways, an exploratory study was conducted on the maximum speed limit at night. In order to investigate the potential relationship between drivers’ distance recognition and driving speed and between speed perception and driving speed under different geometric design features, an experiment was carried out on a 22-km-long freeway segment on Chang-song freeway in China. Based on round-trips made by 10 drivers during day and night on this segment, drivers’ recognition distance (distance between a sign and the location where the sign was clearly recognized the fi rst time) and estimated speed were recorded. The data analysis results show that driver recognition distance at night decreases by about 7% compared with recognition distance at daytime. The accuracy of driver speed perception at nighttime is only 29%, whereas it is 67% at daytime. With the collected data, several multivariate non-linear regression models were established to capture the relationship among the variables of recognition distance, estimated speed at night, driving speed, and highway alignment indexes. Then the modeling results were used to develop the speed limit model by physical equations. A case study is introduced at the end of the paper.
freeway, traffi c safety, nighttime, recognition distance, estimated speed, maximum speed limit.
 Konstantopoulos, P., Chapman, P. & Crundall, D., Driver’s visual attention as a func-tion of driving experience and visibility: using a driving simulator to explore drivers’ eye movements in day, night and rain driving. Accident Analysis and Prevention, 42(3), pp. 827–834, 2010. doi: http://dx.doi.org/10.1016/j.aap.2009.09.022
 Easa, S.M., Reed, M.J., Russo, F., Dabbour, E., Mehmood, A. & Curtis, K., Effect of increasing road light luminance on night driving performance of older adults. International Journal of Engineering and Applied Sciences, 6(1), pp. 41–48, 2010.
 Babizhayev, M.A., Minasyan, H. & Richer, S.P., Cataract halos: a driving hazard in aging populations. Implication of the Halometer DG test for assessment of intraocular light scatter. Applied Ergonomics, 40(3), pp. 545–553, 2009. doi: http://dx.doi. org/10.1016/j.apergo.2007.09.003
 Hua, W. & Donnell, E.T., Models of acceleration and deceleration rates on a com-plex two-lane rural highway: results from a night driving experiment. Transportation R esearch Part F, 13(6), pp. 397–408, 2010. doi: http://dx.doi.org/10.1016/j. trf.2010.06.005
 Horberry, T., Anderson, J. & Regan, M.A., The possible safety benefi ts of enhanced road markings: a driving simulator evaluation. Transportation Research Part F, 9(1), pp. 77–87, 2006. doi: http://dx.doi.org/10.1016/j.trf.2005.09.002
 Baker, R.G.V., On the quantum mechanics of optic fl ow and its application to driving in uncertain environments. Transportation Research Part F, 2(1), pp. 27–53, 1999. doi: http://dx.doi.org/10.1016/S1369-8478(99)00005-4
 Campbell, J.L., Richard, C.M. & Brown, J.L., Chapter 17: speed perception, speed choice, and speed control. NCHRP Report 600C: Human Factors Guidelines for Road Systems, Transportation Research Board, Washington, D.C, 2010.
 Suh, W., Park, P.Y.J., Park, C.H. & Chon, K.S., Relationship between speed, lateral placement, and drivers’ eye movement at two-lane rural highways. Journal of Transportation Engineering, 132(8), pp. 649–653, 2006. doi: http://dx.doi.org/10.1061/ (ASCE)0733-947X(2006)132:8(649)
 Henriette, W.W., Türker, Ö. & Timo, L., Cross-cultural differences in drivers’ speed choice. Accident Analysis and Prevention, 41(4), pp. 816–819, 2009. doi: http://dx.doi. org/10.1016/j.aap.2009.04.004
 Pasetto, M. & Manganaro, A., Night speed negotiation on rural road s-shaped curves: discussion of an experimental case-study. Proceedings of the Fifth International Driving Symposium on Human Factors in Driver Assessment, Training and Vehicle Design, pp. 475–481, 2009.
 Mannering, F., An empirical analysis of driver perceptions of the relationship between speed limits and safety. Transportation Research Part F, 12(2), pp. 99–106, 2009. doi: