The use of colored pavements for bicycle facilities represents an interesting strategy for supporting the implementation of a high-quality cycling network. The distinctive coloration of dedicated ...lanes, tracks or shared paths provides a clearly delineated route, making the infrastructure more attractive as well as legible and intuitive, especially through intersections and junctions. The additional emphasis resulting from the coloring enhances a change in the road users' behavior, but its safety effectiveness seems to be particularly related to several site-specific contextual features. Although some of these benefits are well established and multiple applications of colored pavements are widespread around the world, most of cycling design standards and guides, which are usually written only in the language of the country that drafted them and are often difficult to find, completely lack in technical recommendations and concepts regarding the use of color for cycling provisions. Thus, based on an extensive worldwide literature search from more than 80 official design guidelines, manuals and standards and 50 scientific articles, the authors have structured a guided overview of the state of the art/practice concerning the use of color for bike facilities at the international level, including the latest innovative and experimental schemes. The review is not intended to be a summary of manuals, but is conceived as a decision-makers’ and designers’ tool for a rational planning, construction, maintenance and management of colored cycling infrastructures, able to favor a cultural and technical interchange. After a first section in which the main locations where to use colored surfaces were highlighted (corridor or spot treatments), the commonly used colors (red, green and blue) have been identified, explaining the hierarchical and/or combined reasons (regulatory and legal limitations, visual-perceptual aspects and application/maintenance requirements) behind this choice. Finally, the different coloring techniques associated with the pavement materials have been described.
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•Color may be applied along dedicated bike lanes/tracks or only on potential conflict zones.•Different shades of red, green and blue are adopted worldwide for bicycle facilities.•Standards for color in cycling infrastructures are rarely established at a national level.•The choice of color depends on regulatory limitations, visual-perceptual aspects and application/maintenance requirements.•Colored pavements require a fully-fledged design and maintenance planning.
Objective: Safety performance at bus stops is generally evaluated by using historical traffic crash data or traffic conflict data. However, in China, it is quite difficult to obtain such data mainly ...due to the lack of traffic data management and organizational issues. In light of this, the primary objective of this study is to develop a quantitative approach to evaluate bus stop safety performance.
Methods: The concept of level-of-safety for bus stops is introduced and corresponding models are proposed to quantify safety levels, which consider conflict points, traffic factors, geometric characteristics, traffic signs and markings, pavement conditions, and lighting conditions. Principal component analysis and k-means clustering methods were used to model and quantify safety levels for bus stops.
Results: A case study was conducted to show the applicability of the proposed model with data collected from 46 samples for the 7 most common types of bus stops in China, using 32 of the samples for modeling and 14 samples for illustration. Based on the case study, 6 levels of safety for bus stops were defined. Finally, a linear regression analysis between safety levels and the number of traffic conflicts showed that they had a strong relationship (R
2
value of 0.908).
Conclusions: The results indicated that the method was well validated and could be practically used for the analysis and evaluation of bus stop safety in China. The proposed model was relatively easy to implement without the requirement of traffic crash data and/or traffic conflict data. In addition, with the proposed method, it was feasible to evaluate countermeasures to improve bus stop safety (e.g., exclusive bus lanes).
The paper introduces a new notion that is a graph of crossroad transport flows. It has been shown that the given graph serves as a unification of conflict graphs. The paper provides numerical ...characteristics of graphs on conflict interaction of transport flows in the process of their merging and intersection at crossroads of various configuration. The following construction of the graph has been carried out: merging graphs where their nodes correspond to conflicting flows and their edges indicate what flows enter into a merging conflict between themselves; intersection graphs where graph nodes correspond to conflicting flows and their edges indicate what flows enter into an intersection conflict between themselves. Taking into account the conflict interaction between traffic and pedestrian flows, traffic conditions and traffic trajectories before possible physical interaction the traffic flow graph takes such form which contains complete information about existing conflicts for the required intersection. As a result of the construction in accordance with theoretical aspects of a graph theory and actual interaction of transport and pedestrian flows at intersections, some regularities have been revealed that allow to estimate a danger of any particular intersection within the urban street-road network. The proposals can be identified as hazard markers of an object and that is especially topical with due account of available actual data on driving regimes, traffic light regulation, flow intensity and driving speed (especially single vehicles exceeding permissible driving speed for urban traffic or taking into account local restrictions on certain sections of street-road network) which form a vehicle or pedestrian graph. The proposed approaches can be used to assess quality of road traffic in conflict areas of the street-road network in cities and settlements and public roads as well.
Analysis of intersection delay is important for intersection signal timing. Based on the gap acceptance theory, the conflict point delay of left-turning vehicles crossing opposing flow in mixed ...traffic at two phases signal control intersections is set up with probability theory. Observed values of conflict point delay of left-turning vehicles are compared with the calculated values from the model by choosing some certain intersections in Nanjing. Relationships among conflict point delay of left- turning vehicles, volume of opposing flow and composition of left-turning vehicles has been analyzed. The result shows that the model accords with the actual traffic flow condition at a two phases signal control intersection.
Hardware Transactional Memory (HTM) systems implement version management and conflict detection in hardware to guarantee that each transaction is atomic and executes in isolation. In general, HTM ...implementations fall into two categories, namely, eager systems and lazy systems. Lazy systems have been shown to exploit more concurrency from potentially conflicting transactions. However, lazy systems manage a transaction's entire write set lazily, which gives rise to two main disadvantages: (a) a complex cache protocol and implementation are required to maintain the speculative modifications, and, (b) the latency of committing the entire write set often leads to severe performance degradation of the whole system. It is observed in a wide range of workloads that more than 55% of the transaction aborts are due to conflicts on only three memory blocks. Thus we argue that an eager HTM system can achieve the same level of concurrency as lazy systems by managing only a small portion of a transaction's write set lazily. In this paper, we present Selective-Eager-Lazy HTM (SEL-TM), a new HTM implementation to adopt complementary version management schemes within a transaction whose write set is divided into eagerly- and lazily-managed memory addresses at runtime. An intelligent hardware scheme is designed to select the memory addresses for lazy management as well as determining whether each dynamic instance of a transaction benefits from hybrid management. Experimental results using the STAMP benchmarks show that, on average, SEL-TM improves performance by 14% over an eager system and 22% over a lazy system. The speedup demonstrates that our design is capable of harvesting the concurrency benefit of lazy version management while avoiding some of the performance penalties in lazy HTMs.
Method of traffic organization in signalized intersection with straight waiting area has been analyzed, containing the comparison between the channelization of the left-turn waiting area and that of ...the straight waiting area, ways of signal controlling and the potential operating efficiency. Then, focusing on the influences on the capacity of the intersection containing the straight-right-mixed lane with the straight waiting area, a model of the impact of the vehicle delay on the intersection when setting straight waiting area and a model of the conflict points have been established. The intersection of Zhongshan Road, Hongqiao Road, Shanghai, as an example, through the actual survey data of delay and conflict verifies the effectiveness of the models. The result is that compared to without the straight waiting area, the delay in west road is reduced by 5.6%. Setting straight waiting area may not only improve the traffic capacity, but also influence intersection safety. This measure is effective especially for the intersection with a straight-right-mixed lane and a large number of non-motor vehicles and pedestrian.
In order to study the capacity of vehicles at conflict points in intersections, and to obtain the passing flow rate of the two conflict streams, this paper provides an in-depth analysis of the ...dynamic characteristics of vehicles at the conflict points, as well as the two major parameters - the time headway and the critical gap. Microscopic simulation is used to achieve qualitative analysis of the vehicles capacity at conflict points, which demonstrates the basic characters of the vehicles capacity at conflict points.
This paper applies the principle of vehicle dynamics and traffic conflict theory to analyze the driver behaviors and speed of next two vehicles with green lights. Based on the analysis, we propose ...the smallest calculation formula of green change interval which ensure vehicles cross intersection safely. Combining with traffic psychology, we study the impact of signal countdown device to green change interval which is the key security factor of intersection and analyze the safety efficiency of signal countdown device. At last, the conclusions are given.
In signal control theory, how to appropriately evaluate the lost time is an important issue because it affects the determination of the cycle time. In terms of vehicle trajectory data observed at ...different intersections, the research considers the evaluation of the all red time focusing on the conflict points and calculates it properly using the saturation flow rate. In conclusion, it showed that the lost time could be shortened using conflict point analysis methodology and a more accurate acquisition of the saturation flow rate is very important for the proper estimation of lost time in its application.
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