Multi-Purpose ESS/ITS Data Collection Sites

This document presents the results of a state-of-practice survey of transportation agencies that are installing intelligent transportation sensors (ITS) and other devices along with their environmental sensing stations (ESS) also referred to as roadway weather information system (RWIS) assets

Vertical Delineation

Vertical delineators are intended to warn drivers of an approaching curve while providing them with a better appreciation of the sharpness of a curve. Drivers can then select an appropriate speed before entering the curve. Delineation can also provide continuous tracking information once drivers are within the curve to help position their vehicles within the travel lane while traversing the curve. The most common type of vertical delineation is post mounted delineators (PMDs). These devices are usually flexible or rigid posts with some amount of reflective surface mounted along the roadside to provide additional delineation. Another treatment that has been used is to provide additional delineation on chevron posts

Chevrons and Oversized Chevrons

Chevrons provide additional empha­sis and guidance for drivers. If spaced properly, chevrons can delineate the curve so drivers can interpret the sharp­ness of the curve. Table 2C-2 of the Manual on Uniform Traffic Control Devices (FHWA 2009a) recommends the size of chevron alignment (W1-8) signs by roadway type. Several agencies, including the Iowa Department of Transportation (Iowa DOT), have applied a larger chevron size to a roadway than suggested by this table. The idea is that larger chevrons will be more prominent and visible to drivers. These larger chev­rons may be particularly useful if sight distance issues exist

On-Pavement Signing

Pavement marking legends are placed on the roadway to remind drivers of the speed limit or to slow down. Use of wording on the pavement surface is more dramatic than use of signing only, which can get lost in the clutter of a streetscape. On-pavement speed limit markings have been used to reinforce speed limits or to indicate a transition zone. For more on this topic by these authors, see also Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project : http://www.trb.org/main/blurbs/172092.asp

Roadway Lighting and Safety: Phase II - Monitoring Quality, Durability, and Efficiency

This Phase II project follows a previous project titled Strategies to Address Nighttime Crashes at Rural, Unsignalized Intersections. Based on the results of the previous study, the Iowa Highway Research Board (IHRB) indicated interest in pursuing further research to address the quality of lighting, rather than just the presence of light, with respect to safety. The research team supplemented the literature review from the previous study, specifically addressing lighting level in terms of measurement, the relationship between light levels and safety, and lamp durability and efficiency. The Center for Transportation Research and Education (CTRE) teamed with a national research leader in roadway lighting, Virginia Tech Transportation Institute (VTTI) to collect the data. An integral instrument to the data collection efforts was the creation of the Roadway Monitoring System (RMS). The RMS allowed the research team to collect lighting data and approach information for each rural intersection identified in the previous phase. After data cleanup, the final data set contained illuminance data for 101 lighted intersections (of 137 lighted intersections in the first study). Data analysis included a robust statistical analysis based on Bayesian techniques. Average illuminance, average glare, and average uniformity ratio values were used to classify quality of lighting at the intersections

Measuring Salt Retention

This research developed and completed a field evaluation of salt distribution equipment. The evaluation provides a direct comparison of three different types of salt spreaders at three different truck speeds and brine rates. A rubber mat was divided into eight sample areas to measure the salt distribution across the lane by each variable combination. A total of 264 samples were processed and measured. These results will support future efforts to target areas of efficiencies specific to salt and brine delivery methods. These results support Iowa Department of Transportation efforts to progress winter maintenance efficiencies and ultimately motorist safety

Evaluating the Effectiveness of Temporary Work-Zone Pavement Marking Products

BACKGROUND Work zones by nature present transitions and changes to motorists’ expectations. Given these conditions, providing proper guidance to motorists is critical. With respect to pavement markings, the challenge is to provide sufficient markings but in a temporary setting. Various pavement-marking products are currently in use within work zones; however, their effectiveness and cost can vary widely. OBJECTIVE This research evaluated the effectiveness of several common removable pavement marking products in terms of daytime presence, retroreflectivity, and removability. METHODOLOGYThe work zone pavement marking evaluation was organized into three tasks as follows: Work with industry to identify the available products specific to removable tapes having a wet night retroreflective and/or wet recoverable feature Acquire these products and coordinate installation with a local contractor for a central Iowa work zone Monitor and measure performance in terms of durability (presence and retroreflectivity) and removal The pavement marking evaluation was completed on an active work zone in central Iowa with the roadway setting and performance duration defined by the project. The desire was to select a project that would leave the markings in place for at least 30 days and have sufficient average daily traffic to provide an evaluation of wear. The evaluation included both white and yellow edge-line markings within the taper and crossover sections of a work zone. Performance was measured in terms of presence, retroreflectivity, and ease of removal. Presence was evaluated in terms of the amount of product remaining at the end of the evaluation period. Retroreflectivity was measured using a 30 meter geometry retroreflectometer. Product removal was evaluated in terms of internal tape strength, adhesive bond, and the amount of discernible markings after removal based on the American Association of State Highway and Transportation Officials (AASHTO) National Transportation Product Evaluation Program (NTPEP)

Center Island with Raised Curbing for Rural Traffic Calming

Small rural communities often lack the expertise and resources necessary to address speeding and the persistent challenge of slowing high-speed through traffic. The entrances to communities are especially problematic given that drivers must transition from a high-speed, often-rural roadway setting to a low-speed community setting. A number of traffic-calming devices were evaluated to determine their effectiveness in reducing speeds along the main road through a small rural community. Five different treatments were selected and installed in six rural Iowa communities. This tech brief highlights use of temporary curbing to create center islands

Transverse Speed Bars for Rural Traffic Calming

Small rural communities often lack the expertise and resources necessary to address speeding and the persistent challenge of slowing high-speed through traffic. The entrances to communities are especially problematic given that drivers must transition from a high-speed, often-rural roadway setting to a low-speed community setting. A number of traffic-calming devices were evaluated to determine their effectiveness in reducing speeds along the main road through a small rural community. Five different treatments were selected and installed in six rural Iowa communities. This tech brief highlights use of transverse speed bars