There was a lot of discussion about roundabouts at Tuesday’s City Council meeting, and most of the information came from a report written by the City’s Public Works department. I acquired a copy of the report, and found it well-written and persuasive:
Allen Road and Hickory Grove Road Intersection Improvement
Construction Costs
Farnsworth Group, as a consultant for the Dunlap School Board, was asked to develop a cost estimate for the Allen Road and Hickory Grove Road Intersection improvement to compare the costs of a roundabout with a traditional four-way stop intersection. They responded with a concept cost estimate for the intersection. The design costs for the roundabout were slightly higher because of the complexity of the intersection and the desire to have an outside firm, Ourston Roundabout Engineering Inc., perform an independent review. The construction cost for the traditional intersection was slightly higher because of the need for turn lanes at the intersection. The overall design and construction cost for the two concepts were approximately equal, at about 1.2 million dollars each.
Future Costs
The traffic study performed by Farnsworth Group shows that in the construction year, 2012, the intersection does not meet warrants for the installation of a traffic signal. However, the traffic study shows that within 10 years this intersection will warrant traffic signals, which will be necessary to ensure safe and efficient traffic flow for the school. The design and construction of a traffic signal would cost between $250,000 and $300,000 and may include additional right-of-way. A single lane roundabout will be adequate to handle the increase of traffic at this intersection long past the point that traffic signals are warranted, even past the 20 year design done by the consultants, so no future construction costs are foreseen with this design.
Maintenance and Operating Cost
The maintenance and operating cost of a roundabout and a traditional four-way stop intersection would be approximately the same. Both would require lighting and periodic paint striping. The landscaping maintenance for a roundabout may be slightly higher, but staff would suggest that the central island of the roundabout be established with low maintenance landscaping when constructed. Once traffic signals are installed at this intersection the City can expect and average operating and maintenance obligation of approximately $2500 per year for this intersection. No future increase in maintenance and operating cost would be required for the roundabout design.
Other Roundabout Considerations
Vehicle Safety
Roundabouts have been shown to be safer than traditional intersections. A roundabout has decreased conflict points for traffic, only 8, as compared to 32 in a traditional intersection. With a large central island all traffic must enter to the right, which virtually eliminates severe head-on and right angle crashes. According to a blog post from Regan Zambri Long, all traffic in the roundabout travels slowly in one direction, which reduces speeds, which further reduces crash severity of truck accidents. Studies have shown that roundabouts decrease total crashes by nearly 40%, injury crashes by nearly 80% and fatal crashes by nearly 90% over a traditional style intersection. There are also plenty of semi-truck accident attorneys that can help make a case for you if you find yourself in an accident involving one.
Pedestrian Safety
The design of a roundabout includes splitter islands, which separate entering and exiting traffic. These slow traffic entering the roundabout. The splitter islands also serve to provide pedestrians and bicyclists a refuge when crossing the roadway. Pedestrian only have to watch for traffic in one direction at a time. Often, when a traditional intersection has dedicated turn lanes, a single lane roundabout design will have shorter pedestrian crossing distances and reduced vehicle/pedestrian conflict points.
Traffic Capacity
A single lane roundabout will accommodate traffic that exceeds warrants for traffic signals. This will eliminate the need for intersection upgrades for the foreseeable future.
Traffic Delay
Studies have shown that roundabouts reduce intersection delay by nearly 70% compared to four-way stop or signalized intersections. Using the traffic study figures for the Allen Road and Hickory Grove Road Intersection, staff has estimated a 10 second per vehicle delay reduction. For the construction year this results in an estimated annual savings of over 320 days of lost time by the drivers using the intersection. Putting a modest value of $10 per hour for this time, a cost of over $76,000 per year in lost time is seen for drivers. This amount will increase as traffic volumes increase.
Fuel Consumption
Reducing traffic delay has the added benefit of reducing fuel consumption at the intersection. A small decrease in delay can lead to a surprisingly large reduction in fuel. At a rate of fuel consumption of 1.2 gallon per hour of idling, nearly 10,000 gallons of fuel could be saved at Allen Road and Hickory Grove Road with the installation of a roundabout, instead of a four-way stop. With gas nearing $4 a gallon, this leads to a savings of nearly $40,000 for drivers. This figure increases with traffic volume, with of over 13,000 gallons of fuel savings per year estimated over a four-way stop at this intersection in 2022.
Emissions Reduction
A reduction in traffic delay can also be beneficial in reducing harmful vehicle emissions. This is especially important because the Peoria area is nearing the threshold of the EPA’s air attainment levels. Additionally, the EPA is considering lowering this threshold. Studies have shown an emissions reduction of 20-30% for a roundabout over a traditional intersection. Staff research gave us an estimate of 19 lbs of CO2 produced per gallon of gas consumed. By saving 10,000 gallons of fuel annually, a roundabout at Allen Road and Hickory Grove Road will reduce the CO2 emissions by 95 tons per year at this intersection. Other types of emissions are also reduced, but are not as easily calculated.
Public Opinion:
Studies have shown that in places that do not have roundabouts that initial public opinion is often negative. This is generally because they are new concepts to local drivers. The public sometimes confuses them for other types of intersections, such as rotaries, neighborhood traffic circles or town centers, (like in Washington Illinois), or they feel that local drivers will not understand them. Studies have also shown that after a roundabout is constructed that the opinions turn positive. One study staff researched showed poll results from before and after the installation of a roundabout. The before results where 68% negative or very negative and the after results were 73% positive or very positive. This shows an almost complete reversal of opinion once the roundabout was constructed.
4/11/11 nas
