course on - freese and nichols, inc. course summer 2010.pdf · modern roundabouts are defined by...
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Modern Roundabouts Make a Comeback in the U.S.What’s a Modern Roundabout?Modern roundabouts are defined by these basic operational and design principles:�� Yield-at-Entry�– Modern roundabouts require that vehicles in the circulatory roadway have the right of way.�� Deflection�for�Entering�Traffic�– No tangential entries are permitted, and no traffic streams get a straight movement through the intersection.
Typical roundabout geometric elements include: � Approach road � Departure road � Central island � Circulatory roadway � Splitter island
Why the Increase in Popularity?Increased safety and lower traffic delays are the primary reasons for the modern roundabout’s recent growth in popularity. According to the New York State Department of Transportation’s Highway Design Manual, roundabouts typically reduce traffic delays anywhere from 30 to 70 percent for the same traffic volumes experienced by a traditional intersection. A study conducted by the Insurance Institute for Highway Safety found that roundabouts result in a “39 percent overall reduction in accidents, a 76 percent reduction in injury accidents, and an 89 percent reduction in fatal or incapacitating accidents.” No other
type of intersection has been found to increase driver safety to a similar degree. In addition, the Federal Highway Administration has determined roundabouts to be “the preferred safety alternative for a wide range of intersections” in a guidance memorandum revised in July 2009.
Pros vs. ConsAs with any engineering project, there are pros and cons to installing modern roundabouts in a community. Pros include:
� Traffic calming capabilities � Aesthetic benefits � Continuous traffic flow � No traffic signal malfunctions or maintenance � 75 percent fewer conflict points (vehicle/vehicle, vehicle/pedestrian, vehicle/bicyclist)
Cons include: � High initial cost due to more roadway work and the need to convert an existing intersection to roundabout instead of a signal
� Public unfamiliarity � More right-of-way needed � More pavement marking and signage needed
Interested? – FNI Can HelpFNI can help determine if a modern roundabout is the solution for your community’s needs. Please feel free to contact any of key contacts listed on Page 2 for more information.
Mehran (Ron) Bavarian, P.E.Pearland Office [email protected]
CourseTransportation Engineering Newsletter
Summer 2010
Summer 2010 01
OnPearland�Parkway�Roundabout,�City�of�Pearland�– FNI provided design for this modern roundabout, which serves as the center point of the marquee entrance into the City of Pearland from the Beltway 8 toll freeway. Construction was completed in 2003.
Down the RoadUpcoming Events
2010 Texas Municipal League 98th Annual Conference and Exhibition, October 26-29, Corpus Christi
6th Annual Texas Transportation Forum, January 3-5, 2011, Austin
Tighter Budgets, New Regulations Call for Low-Impact Storm Water Design for RoadsTighter construction and maintenance budgets and stricter water quality regulations present roadway owners with the challenge of reducing material usage and maintenance requirements, while still considering safety, level of service and environmental impacts. Traditional storm water infrastructure design (pipes, inlets and ditches) attempts to balance safety and cost, while efficiently minimizing significant flooding within a street’s right-of-way. However, it often generates:
� Increased costs (due to installing extensive, oversized underground conduits) � Difficult and, thus, infrequent maintenance (resulting in lost capacity and system efficiency)
� Water quality impacts (due to untreated contaminants transported by first flush runoff)
� Increased erosion and flooding potential downstream of the system
Many roadway owners are moving away from traditional to low-impact storm water design as a viable option for reducing costs and maintenance burdens, while maintaining level of service, safety and/or improving water quality.
Examples of low-impact storm water design include: � Integrating rainwater harvesting and native species planting into the design to conserve water, reduce infrastructure requirements and ease maintenance
� Installing pervious shoulder treatments for roadways without curbs to reduce shoulder erosion and provide treatment of first flush runoff before it enters a drainage ditch or receiving stream
� Diverting first flush flows into curbside bioretention areas
� Using bioswales and bioretention basins in the median or shoulder to capture, treat and convey runoff and reduce underground pipe requirements
� Combining regional detention planning with transportation planning
Please feel free to contact FNI for more information on how to implement low-impact storm water design in your projects.
Mikel Wilkins, P.E., LEED APStorm Water Project [email protected]
02 Summer 2010
Key ContactsFor�more�information�about�our�transportation�services,�please�contact:
Dallas�Tricia Hatley, P.E., LEED [email protected]
Fort�WorthJohn Dewar, P.E., [email protected]
San�Antonio/AustinRichard Kelley, [email protected]
HoustonJeff [email protected]
PearlandMehran (Ron) Bavarian, [email protected]
Corpus�ChristiRon Guzman, [email protected]
For�more�information�about�On Course,�please�contact:Ashley [email protected]
Using bioswales in the median
Integrating rainwater harvesting
Stabilizing Embankment Slopes FAQsOver time, nearly all constructed embankment slopes experience some degree of settlement, also known as soil creep. The following are some common questions and answers to assist your slope embankment maintenance.
How can I tell if a slope is settling?Common indicators of slope settling include: a gap at the edge of the pavement compared to the slope, a sag or lean in the guardrail, a bulge at the toe of the slope, broken structures nearby (culverts, inlets, paved ditches), and leaning retaining walls.
What causes a slope to settle?According to a study completed by Iowa State University in 2004 (CLICK�HERE�to�read�the�full�study), slope settlement is typically caused by a combination of several factors, including seasonal temperature changes, soil erosion, faulty construction, soil settlement and high traffic.
How much settlement is acceptable?Typically, a two-inch settlement in an embankment is acceptable. Anything beyond that can present a safety hazard for drivers.
What if a slope has settled significantly?Once a slope has settled more than two inches, a geotechnical engineer should review the problem. Typically, the sooner a problem is identified, the less complicated and expensive the solution will be. With Texas experiencing record precipitation and temperatures in 2010, it’s a good idea to keep an eye on your embankments to identify and mitigate any existing settling as soon as possible.
How is an unstable slope repaired? There are several methods available to repair unstable slopes. The following are several approaches:1. Modify the slope’s profile (flatten, add berms
and benches).2. Add erosion control blankets and edge drains.3. Remove and replace existing soil with stronger
material, such as fiber reinforced soil (this may be combined with approaches 1 and 2).
4. Stabilize the toe of the slope (place soil mass, install drilled shafts).
5. Install soil nails.6. Construct retaining walls.7. Place geotextiles (although not typically possible,
since it may require anchoring under the roadway).
However, there are also things to avoid: � Excavating the toe of slope � Removing lateral slope support � Placing fill at the top of slope � Blocking drainage paths � Using rigid pipe within slope
Alex Garcia, E.I.T.Transportation [email protected]
Summer 2010 03
FNI was succesful using fiber reinforced soil for the City of Grand Prairie (show above). In this method, all existing soil in the embankment is removed and blended with synthetic fibers to add strength and stability to the soil. The newly-reinforced soil is covered with a geotextile and augmented with horizontal drains to keep the soil well drained.
Pre-Construction
During�Construction
Post�Construction
Ron Bavarian, P.E. is a firm Associate and the Southeast Division Infrastructure Group Manager and Pearland Office Manager at FNI. With 33 years of experience, Ron’s understanding
of municipal management challenges, including regulation, funding, construction management and long-term maintenance, has made him an experienced resource for helping municipalities analyze and prioritize infrastructure needs, particularly in roadway and utility design.
Also an effective project manager, Ron is experienced in managing high-profile, multi-discipline projects that have garnered both client appreciation and professional recognition. Ron’s general project management experience includes
roadways, drainage facilities, lift stations, utilities, and water and wastewater treatment plants for municipalities. He also has developed solutions for the complex design challenges of roundabouts, overpasses, signalization, intersections, storm water facilities, utility relocations, right-of-way acquisitions and multi-agency coordination and approvals.
Ron’s professional accomplishments reflect his dedication to delivering lasting value to FNI’s clients. Ron and his wife, Forouz, who also works as a Transportation and Utilities Technician at FNI, work and live in Pearland. They have two grown children, Christine and Jason.
Contact InformationPlease feel free to contact Ron at FNI’s Pearland office at 832-456-4722 or [email protected].
Introducing: Mehran (Ron) Bavarian, P.E.
04 Summer 2010
Three-Year Cost Inflation for Highway and Street Construction
» The Highway and Street Construction Cost Index (above) is based on an established package of goods related to road construction. In June 1986, this package, which includes cost of materials and labor, was valued at $100.
» Between May 2003 and July 2008, highway and street construction costs increased 77.7 percent.
» Since prices peaked in July 2008, highway and street construction costs have decreased 10.9 percent.
180.0
185.0
190.0
195.0
200.0
205.0
210.0
215.0
220.0
225.0
230.0
235.0
240.0
245.0
* Figures from the Bureau of Labor and Statistics* March 2010 to present PPI Data are Preliminary Figures
8.5% IncreaseJuly '07 -June '10
10.9% Decrease since Peak Pricing
July '08 - June '10