## 4 Suitability Evaluation and Effect Analysis of Non-Conventional Lanes  
### Analysis of Applicable Conditions  
Suitability evaluation of non-conventional lanes is a key issue in resolving \"when and where\" to implement non-conventional lanes. Existing research has achieved rich resultsin evaluating the effects of different types of non-conventional lanes, but studies on their applicability to diverse urban road characteristics still need to be deepened.  
[PERSON] et al. [59] proposed robust optimization methods to determine lane allocation schemes, establishing a two-level stochastic model to obtain robust lane allocations less sensitive to traffic flow fluctuations. [PERSON] et al. [60] explored symmetric intersection design innovations, significantly increasing intersection capacity through innovative geometric layouts and three-phase signal control. [PERSON] et al. [61] analyzed the operational advantages of contraflow left-turn lane (CLL) design, demonstrating through simulation analysis that CLL can increase capacity and reduce delay.  
From a systematic analysis of applicable conditions, the implementation of non-conventional lanes needs to consider multiple factors: traffic demand characteristics (volume, directional distribution, time-varying characteristics), geometric conditions (spatial constraints, number of lanes, median width), traffic composition (proportion of large vehicles, proportion of non-motorized vehicles), and driver characteristics (familiarity level, compliance rate), among others. For example, contraflow left-turn lanes are suitable for intersections with high left-turn demand (typically greater than 30%) and where opposing exit lanes have surplus capacity; outside left-turn lanes are more suitable for special scenarios such as under elevated ramps and entrances/exits of large commercial facilities; variable lanes are suitable for roads with significant time-varying traffic flow characteristics, and U-turn designs are suitable for arterial roads with high traffic volumes and sufficient median width.  
Analysis of applicable conditions provides a decision-making basis for the scientific implementation of non-conventional lanes. Based on the systematic analysis of the reviewed literature, evidence-based implementation guidance can be synthesized from documented research findings. Contraflow left-turn lanes demonstrate effectiveness when left-turn ratios exceed 30% and opposing exit lanes have surplus capacity, as documented by [PERSON] et al. [9], with field studies showing 42.9% driver adoption rates under proper implementation conditions [10]. Outside left-turn lanes prove most suitable under elevated ramps and at commercial facility access points where adequate weaving distances exist [16; 18]. Variable and reversible lanes require significant directional traffic imbalance and reliable enforcement systems, with dynamic control achieving a 27.4% delay reduction compared to fixed timing approaches [25]. The performance expectations derived from reviewed studies indicate contraflow designs can achieve 20-30% capacity increases [9], tandem intersections typically reduce delays by approximately 20% [34], and properly implemented outside left-turn lanes demonstrate 21.8% safety improvement over conventional designs [17]. However, the consistent finding across all studies is that actual field performance often falls 15-25% below simulation predictions when driver education, enforcement capabilities, and geometric constraints are inadequately addressed during implementation.  
At the same time, there is a need to develop intelligent decision support systems capable of dynamically assessing the suitability of non-conventional lanes based on real-time traffic data and prediction information, providing scientific decision support for traffic managers. Furthermore, considering the dynamic nature of urban development, applicable conditions should also incorporate time dimensions, establishing adaptive evaluation and dynamic adjustment mechanisms.