This paper evaluates the traffic safety of freeway interchange merging areas based on the traffic conflict technique. The hourly composite risk indexes (HCRI) was defined. By the use of unmanned aerial vehicle (UAV) photography and video processing techniques, the conflict type and severity was judged. Time to collision (TTC) was determined with the traffic conflict evaluation index. Then, the TTC severity threshold was determined. Quantizing the weight of the conflict by direct losses of different severities of freeway traffic accidents, the calculated weight of the HCRI can be obtained. Calibration of the relevant parameters of the micro-simulation simulator VISSIM is conducted by the travel time according to the field data. Variables are placed into orthogonal tables at different levels. On the basis of this table, the trajectory file of every traffic condition is simulated, and then submitted into a surrogate safety assessment model (SSAM), identifying the number of hourly traffic conflicts in the merging area, a statistic of HCRI. Moreover, the multivariate linear regression model was presented and validated to study the relationship between HCRI and the influencing variables. A comparison between the HCRI model and the hourly conflicts ratio (HCR), without weight, shows that the HCRI model fitting degree was obviously higher than the HCR. This will be a reference to design and implement operational planners.

The problem of matching measured flight position points to air routes is definitely important to improve data processing tools that can assist air traffic controllers in analyzing operational situations and making control decisions. This paper proposes a simple map matching algorithm that uses a hidden Markov model (HMM) to find the most likely flight path according to the flight trajectory. The algorithm is tested on real data collected from air traffic control systems. In addition, the correct matching percentage of different sampling-rate data is tested. The HMM works efficiently on conditions where a data preprocessing method is utilized and matches with an error less than 1%.

The upgrade freeway section is an accident-prone roadway segments. This paper studied the operation characteristics of traffic flow on the upgrade section using VISSIM simulation software based on the survey data. The speed standard deviation coefficient (Cv) and the average changing times between car and large vehicles were selected as the indexes to evaluate the impact of large vehicles on traffic safety along upgrade sections and the changes of different slopes and traffic conditions were analyzed. The result shows that the traffic volume and large vehicle mixed rate both affect traffic safety performance on the upgrade section. The upgrade section safety was divided into 3 categories by the speed standard deviation coefficient. The results could provide the improvement guidance for traffic facilities to ensure traffic safety on the upgrade section.

A traffic safety prediction model for the freeway interchange diverging area was established based on traffic conflict technology. Traffic conflict technology is a traditional, non-accident traffic safety evaluation method in which time to collision (TTC) is determined by a traffic conflict evaluation index. Using unmanned aerial vehicle (UAV) photography and video processing techniques, both the conflict type and the severity were obtained. By quantifying the weightings of conflicts as a result of direct economic losses for different severities of freeway traffic accidents, the hourly comprehensive risk conflict index (HCRI) can be obtained. A statistical model was then established under different road and traffic conditions and for TTCs corresponding to different conflict types of different severities. The total HCRI of the diverging area was then weighted. The HCRI risk grade was then classified according to the “σ method.” The evaluation method for traffic safety in the diverging area was verified for the Lindong interchange in China, and the result was classified as general dangerous.