Minor Intersection Research Articles

Evaluation of Auxiliary Signing for Driveway Assistance Devices at Low-Volume Access Points within One-Lane, Bidirectional Work Zones

Work zone traffic control presents unique challenges during single-lane closures on two-lane, two-way facilities. In these circumstances, traffic regulators (i.e., flaggers or temporary signals) ensure alternating one-way travel in the work zone. However, the use of traffic regulators becomes less practical at mid-segment low-volume access points, such as driveways and minor intersections, within the lane closure. These locations present additional risk for flaggers and, owing to financial infeasibility, are often rendered without traffic control. A recently developed experimental traffic control treatment, the driveway assistance device (DAD), is designed to provide guidance to motorists for a safe entrance into the lane closure from low-volume access points. As this device is relatively new, much is still unknown about the optimal device design and operation to provide the highest compliance. To address this, a field study was performed to evaluate driver compliance associated with DADs implemented at a series of driveways along a one-lane, two-way work zone along a state highway in northern Michigan. As little guidance exists for DAD auxiliary signage, the field study specifically sought to compare the effects of five different sign messages utilized with the DAD. The driver compliance data revealed that the most effective sign messages were those that included “Turn” instead of “Yield,” a prominent “WAIT” message at the top, in addition to a supplemental “No Turn on Red” sign. Based on these findings, DADs are recommended for continued experimental use along with appropriate auxiliary signage at work zones where one-lane, two-way traffic is being maintained.

A multi-path arterial progression model with variable signal structures

Over years of development, arterial progression has become a tool of great practicality. However, in regard to multiple paths, no current work is focused on providing green-bands and allowing signal plans to convert between patterns of different structures, putting aside sequence change. Also, the demand of a common cycle length also increases the delay at major–minor intersections. Thus, two multi-path arterial progression models are proposed in this paper, which choose the signal structure of each intersection from several customised options. The only difference is whether consistent widths are required. By choosing signal structures from a given set, the models can alleviate the competing nature of multiple paths. It is noteworthy that the structure-choosing mechanism enables the models to consider double cycle and uneven double cycle plans at major–minor intersections. As experiments manifest, the models are more capable of coping with certain scenarios that previous models may find challenging.

Leveraging Fully Actuated Signal Coordination and Phase Reservice to Facilitate Signal Timing Practices

Signal coordination has been deemed an effective means of improving arterial traffic operations; however, it may cause signal controllers to dwell in coordinated phases regardless of actual traffic demand, resulting in increased delay and unfavorable waiting for the minor-movement traffic. This paper proposes a strategy to facilitate such signal timing practices by actuating the coordinated phase, known as fully actuated coordination, and enabling phase reservice. The actuated coordinated phase can terminate early in response to traffic actuations with minimal influence on arterial progression, and phase reservice allows for a flexible order of phase service, which can lead to an effective re-allocation of the remaining green time after the coordinated phase gaps out. The proposed improvements focus on the situation where traffic volume is low to moderate whereas the coordination cycle length has to be relatively long, such as applying signal coordination at a minor intersection or during the late-night period (e.g., between 9 p.m. and 5 a.m.). The performance of the proposed strategy is explored through hardware-in-the-loop simulation. The simulation results indicate that, as compared with conventional signal coordination, the proposed strategy can achieve a reduction in the overall delay on the non-coordinated movements while the number of stops along the arterial would not significantly increase. Other benefits can also be observed in simulation, for example, speeding control during the late-night period. In addition, the determination of the non-actuated portion of the coordinated phase is studied.

The Effect of Modifying Double Continuous Flow Intersections Layout Geometric Features on their Operation

Introduction: Continuous flow interventions were first introduced as an alternative to improve traffic operations in the intersections with severe congestion caused by heavy left-turn movements. Objective: This study quantified the effect of modifying the intersection angles of Double Continuous Flow Intersections (DCFI) on their operational characteristics. Mainly, the effects of changing the intersection angle between the different approaches of the main intersection and the angle of the minor cross-over intersections were investigated. Methods: VISSIM software simulation models were used for modifying several design features related to the DCFI and the operational performance was compared between the different simulation scenarios. Results and Discussion: Changes to the cross-over intersection angle increase the safety levels by providing better channelization of traffic movements on the minor intersections of the DCFI and reduce the intersection footprint to be used at high-density urban locations. Increasing the cross-over intersection angle and changing the layout geometry have adverse effects on the capacity of the conventional DCFI. This is mainly because of the added curvature in the intersection approaches which reduces the vehicle speeds, therefore reducing the overall capacity of the modified intersection when compared to the conventional DCFI. However, the total footprint for the intersection is reduced for the modified layout geometry, which improves the capacity of the DCFI. Conclusion: The study has explored the effects of modifying the DCFI intersection angles to fit the limited space in major urban areas on the capacity and performance of the intersection. It showed that DCFI designs could be applied in areas with limited space availability and skewed intersection angles.

Characteristics of the close to home crash

Crashes are over-represented on roads close to home, but it is not clear why. We sought to address this gap by exploring the characteristics of close to home crashes. We used twelve months of crash data that included driver home address, and travel survey data captured over the same period to group crashes based on equivalent amounts of travel at different distances from home, controlling for exposure. We compared crashes on high-speed (rural) and low-speed (urban) roads; crashes caused by different types of error (lapse and violation); and crashes at major intersections (roundabouts and traffic signals), minor intersections (priority intersections and driveways), and midblocks; to find out which road type, error type, and locations were most common in crashes on roads close to home. Findings revealed that crashes over-represented close to home were on low-speed (urban) roads; were more likely to involve lapses of attention than violations; and that crashes related to lapses of attention on low-speed roads were more common at minor intersections and mid-blocks than at major intersections. Although drivers may be most likely to consider busy intersections risky and worthy of effortful focus, these results show that seemingly safe, slow streets and minor intersections account for a surprisingly high proportion of crashes overall, particularly on familiar urban roads close to home. The interplay of drivers’ attentional regulation with momentary driving demands, and risk is complex and worthy of continued investigation.

Arterial signal coordination with uneven double cycling

In arterial coordination, high traffic volume at large intersections often requires a long cycle length to achieve good two-way progression. This long cycle length, however, often causes excessive delay at some minor intersections where the traffic volume is low on cross streets. This paper describes optimization models developed to enable uneven double cycling (UDC) in arterial signal coordination to address this issue. The control scheme adopts UDC at some of the minor intersections where a background cycle has two sub-cycles of different lengths. Two multi-objective UDC models are developed. The basic UDC model maximizes constant two-way bandwidths and minimizes average delay of through traffic on cross streets at UDC intersections. This model is then improved by maximizing variable bandwidth and considering pedestrian needs. The resultant models are a mixed integer quadratic programming (MIQP) problem. Results of numerical experiments and case study simulations indicate that the UDC control scheme can greatly reduce delay at UDC intersections without affecting progression quality of arterial through traffic. Preliminary guidelines are also provided for UDC implementation.

Measuring traffic congestion: An approach based on learning weighted inequality, spread and aggregation indices from comparison data

As cities increase in size, governments and councils face the problem of designing infrastructure and approaches to traffic management that alleviate congestion. The problem of objectively measuring congestion involves taking into account not only the volume of traffic moving throughout a network, but also the inequality or spread of this traffic over major and minor intersections. For modeling such data, we investigate the use of weighted congestion indices based on various aggregation and spread functions. We formulate the weight learning problem for comparison data and use real traffic data obtained from a medium-sized Australian city to evaluate their usefulness.

Major urban road characteristics and injured pedestrians: A representative survey of intersections in Montréal, Quebec.

In urban settings, pedestrian fatalities and injuries are concentrated on major roads. This study aims to describe urban intersections with major roads (arterials and collector roads) and explore the association between intersection characteristics and injured pedestrians. From a stratified random sampling in Montréal, Quebec, 512 intersections were selected and their characteristics collected. The number of injured pedestrians from 1999 to 2008 was obtained from ambulance services. Binomial negative regression models (including IRR: incidence rate ratios) were calculated to determine associations between intersection characteristics and injured pedestrians: i) at all intersections; ii) at intersections with multi-lane roads and iii) at signalized intersections with available vehicle and pedestrian counts. Major intersections had more traffic lanes (3.8 vs. 1.7, p < 0.01) and longer pedestrian crossings (18.8 m vs. 12.7 m, p < 0.01) than minor intersections. Bus stops were also more frequent at these intersections (75% vs. 6%, p < 0.01). Overall, each additional traffic lane was associated with a 75% increase in the number of injured pedestrians (IRR = 1.75; 95% confidence interval [CI] = 1.41-2.18). At intersections with multi-lane roads, a fourth branch (IRR = 2.40; 95% CI = 1.53-3.77), vehicles parked within 5 m of the intersection (IRR = 2.40; 95% CI = 1.64-3.51), and marked crosswalks (IRR = 1.79; 95% CI = 1.08-2.95) significantly increased the number of injured pedestrians. Raised medians had no significant protective effect. The results show that besides traffic and pedestrian volumes, intersection characteristics contribute to pedestrian injuries. The reduction of traffic lanes, parking prohibition near intersections and implementation of appropriate pedestrian refuge areas would improve pedestrian safety.

A probabilistic approach towards a crash risk assessment of urban segments

This paper presents a probabilistic approach to measure the crash risk associated to an urban segment. This approach leads to a hotspot definition and identification using a probabilistic model defining the dependent variable as an indicator of a discrete choice. A binary choice model is used considering a binary dependent variable that differentiates a hotspot from a safe site set by the number of crashes per year per kilometre. The explanatory variables to set similar segments are based on average annual daily traffic, segment length, density of minor intersections. A threshold value for the number of crashes per kilometre is set to distinguish hotspots from safe sites. Based on this classification, a binary model is applied that allows the construction of an ordered site list using the probability of a site being a hotspot. A demonstration of the proposed methodology is provided using urban segment data from Porto, Portugal, covering a five-year period. The results of the binary model show a good fit. To evaluate and compare the probabilistic method with three usual hotspot identification methods described in the Highway Safety Manual, measures are used to test the performance of each method. Depending on the tests, actual data or simulated input, which are usually considered to set the “true” hotspots, were used. In general, the tests results indicate that the binary model performs better than the other three models. Nevertheless, it should be noted that the probabilistic approach provides an outcome that is quite different from the other methods, thus making difficult to ensure a linear comparison with the other methods. Overall, the study shows an alternative to hotspot identification using a risk measure in which the gains are the simplicity, the reliability, and the efficiency of model outcome.

A platoon-based traffic signal timing algorithm for major–minor intersection types

This paper presents a platoon-based traffic signal timing algorithm that reduces traffic delays at major–minor type of intersections. The algorithm reduces traffic delays at intersections by minimizing the interruptions to vehicle platoon movements on the major roads. In this paper, the characteristics of vehicle platoons are discussed, including the key platoon variables and their mathematical distributions. Then the platoon-based traffic signal timing algorithm is illustrated with proposed platoon detector placement and signal control logic. Further, through computer simulations it is shown that the platoon-based algorithm provides better performance at major–minor types of intersections than conventional signal timing algorithms.