How interchange spacing effects drivers' visual performance in high-density interchange groups − a naturalistic driving study.

• The effects of interchange spacing and driving zone on driver visual behavior were assessed. • The insufficient intersection spacing resulted in an increase in mean fixation duration and concentration of horizontal fixation points. • Drivers had lower horizontal sweep amplitude and speed on SSI than on NSI and exhibited higher visual loads. • Pupil change was found to be most relevant to driver visual load. • The visual load on drivers is highest in the ramp zone and the difference in visual load caused by the spacing is most significant in the diversion zone. The aim of this study was to evaluate the effects of interchange spacing on the visual characteristics and visual load of drivers in the exit zone of the urban expressway. A naturalistic driving experiment was conducted in a high-density interchange group on the North Ring Expressway in Chongqing, China. Eye-movement data from 47 participants were collected to assess the pattern of visual performance, seven indicators were selected to characterize drivers' visual characteristics, and the entropy weighting method was used to assess the drivers' visual loads under different interchange spacing and driving zones. The results show that insufficient spacing of the interchange affects drivers' visual behavior and increases their visual load level. The fixation duration for drivers is significantly affected by interchange spacing, with longer fixation duration in the diversion and ramp zones of small-spacing interchanging(SSI). The mean horizontal visual angle of drivers was mainly distributed in the middle of the field of view, and there was a tendency for the overall left side to be shifted under the conditions of SSI, and the mean vertical visual angle was mainly distributed in the nearer part in front of the lanes. In the ramp zone of SSI, the driver's attention to the vehicle dashboard had a significant increase. In normal-spacing interchange(NSI), drivers' horizontal saccade amplitude and speed were higher than those in SSI, and the difference was most significant in the diversion zone. Vertical saccade amplitude and speed of the driver were found to be significantly affected by interchange spacing only in the ramp zone. Drivers' visual load had the highest correlation with pupil variation, and the visual load scores of drivers at SSI were 39.65% and 17.7% higher than at NSI in the diversion and ramp zones, respectively. This study provides valuable insights into the effects of the high-density interchange group on the visual performance of drivers on urban expressways, and the results provide a theoretical basis for the spacing control of interchanges. [ABSTRACT FROM AUTHOR]