Steel slag (SS) is regarded as a potentially promising alternative material for road construction, which could ameliorate the shortage of high-quality aggregate and environmental pollution of SS accumulation simultaneously. However, except for some developed countries, the comprehensive utilization rate of SS in developing countries is particularly limited, especially in road construction. This is attributed to the concerns and uncertainties of environmental and mechanical properties caused by the incorporation of SS into pavement. Therefore, a systematic literature review is conducted to explore the status quo and challenges of SS application in road domain to help develop appropriate utilization strategies. Thanks to the excellent antiabrasion, rich angularity, rough texture, and high hardness, SS aggregate possesses favorable interlocking capability that can be utilized in subgrade, base, and surface course. Additionally, when used in surface, it can be considered as a functional material, for instance for antiskidding, noise reduction, and conductive concrete for crack healing and ice melting. The current investigations are still widely interested in performance verification and expansion treatment, but lack relevant mechanism-based analysis. Further rational studies are required in terms of gelation activation technology, adhesion injury, mesoscale skeleton optimization, evaluation of healing efficiency, and long-term performance. Moreover, the environmental assessments including heavy metal and leachate contaminations are necessary for the adoption of SS in pavement.

Although there have been assorted car-following (CF) models for connected vehicles (CVs), studying their impacts in mixed traffic flow of human-driven vehicles (HVs) and CVs remains a challenge. Considering the multiple front vehicles’ optimal speed changes with memory, this study proposed a new CF model (MVCM model) implemented through vehicle-to-everything (V2X) technology in CVs environment in terms of OVCM (Optimal Velocity Changes with Driving Memory) model. The stability condition of MVCM model was derived through linear stability analysis. Then, the disturbance propagation of MVCM model was compared with that of both classical FVD (Full Velocity Difference) model and MHOVA (Multiple Headway Optimal Velocity and Acceleration) model. Finally, a case study was conducted in VISSIM to analyze the impact of CV (with MVCM model) rates on traffic characteristics, including the average speed, delay time and travel time. Results show that 1) considering more front vehicles’ optimal speed strengthens the stability of traffic flow and the optimal considered vehicle number is 4; 2) MVCM model shows better resistance to disturbance than FVD model; 3) and obtain the same stability with MHOVA model, but with fewer front vehicles considered (only 3); 4) larger rate of CVs leads to higher average speed, smaller average travel time and the delay time of CVs and HVs; and 5) CVs’ positive effects reaches stable when CV rate approaches 0.6.

Porous asphalt (PA) pavement has been widely used in the USA, Europe and Japan for the benefit of quick drainage in rainy days and noise reduction. Its application in China, however, is very limited. A PA pavement section, therefore, was paved in Yan-Tong highway in Jiangsu Province as a trial. Since China has no specifications for the design and construction of PA pavements, the Construction Bureau of Traffic Engineering in Jiangsu Province is very concerned with the field performances of the test section in hope of validating and improving the PA pavement designs. Thus, a five-years tracking programme was launched to collect performance data of the PA section and two control sections, the stone mastic asphalt section and the dense graded asphalt section. The investigation range covers permeability, skid resistance (microtexture level and macrotexture level), rutting, roughness and noise on truck lane, passenger car lane and overtaking lane. The overall assessment is that the three pavement sections provide satisfactory performances over the investigation period. However, the unique merit associated with the PA section, that is to drain the water and reduce noise, witnesses a substantial loss along with time.