neighborhood. Most of the business owners (61.5% of survey respondents) in Topeka, KS felt roundabout addition to their street or neighborhood is either “very good” or “good” On contrary, more than half of the business owners in Newton, KS felt negatively (50% of survey respondents felt “very bad” and 16.7% felt “bad”) toward the roundabout added to their street or neighborhood. In Junction City, KS, about 50% of the business owners felt “very good” for the roundabout added to their street or neighborhood and the remaining 50% of respondents felt “bad”. In Caramel, IN, 35.7% of the business owners felt the roundabout was an “excellent” addition to their street or neighborhood and 35.7% of business owners felt very good, i.e., a total of 71.4% business owners felt either excellent or very good about roundabouts being added to their streets or neighborhoods.
3. Simulation of Business Corridor
As there is no before and after corridor data available for making definite conclusions, a business corridor in
Figure 1. Business owners Responses about the overall feeling of the roundabout added to their street or neighborhood.
Topeka, Kansas is simulated using both SIDRA and VISSIM software to evaluate the impacts of converting several traditional intersections in the corridor to roundabouts. A simulation task of a business corridor is conducted to compare the travel along a corridor with signalized intersections to travel along the same corridor when signalized intersections are substituted with roundabouts. Ariniello have analyzed the impact of construction of four roundabouts along a commercial corridor in Golden, Colorado on businesses and observed a continued growth along the corridor showing that roundabouts are good for businesses  ; businesses along this corridor however were initially skeptical about the positive impacts of these roundabouts construction. As the Wannamaker corridor has similar development patterns in Topeka, KS, it was considered for the task of simulating a business corridor. The Wanamaker corridor (shown in Figure 2) is highly developed with some signalized intersections of Wanamaker Road with other arterials and many unsignalized intersections of Wanamaker Road with local streets and entrances to businesses. Since a before and after study could not be conducted on the Wannamaker corridor, the “after” condition was simulated using both SIDRA and VISSIM software to evaluate the impacts of converting several traditional signalized intersections in the corridor to roundabouts.
Figure 2. Wanamaker corridor in Topeka, Ks. (source: Google maps).
Wanamaker corridor is a highly developed commercial corridor in the western part of Topeka, KS. Although the actual Wannamaker corridor is much longer, only a portion of the corridor from a business entrance north of 12th Street (refer Figure 2) till the intersection of 19th Street and Wanamaker Road (refer Figure 2) is used in this study. There are many number of business entrances along the Wannamaker corridor that are controlled by stop signs. The intersections on Wannamaker Road at Huntoon Street, the on-ramp to I-470, 17th Street, a business entrance at the northeast corner of the West Ridge Mall, and 19th Street are controlled by traffic-actuated signals. Each of the signalized intersections were replaced with roundabout treatment for “after” condition in this study. Businesses entrances that are controlled by stop signs were assumed to be right turn only; in other words, when left turn at a stop sign is prohibited, the vehicle will have to proceed to the next roundabout and take a U-turn to travel in its intended direction. Traffic counts for two one-hour periods at the selected signalized intersections were obtained from the city traffic engineer.
3.1. SIDRA Analysis
SIDRA is an intersection analysis software that is used worldwide for calculating intersection capacity, level of service, and performance analysis for various intersection treatments. SIDRA 5.1 version software was used to compare the performance metrics of the current signalized intersections to what would happen if the current signalized intersections were converted to roundabouts and only right turns were allowed at all other intersections. SIDRA intersection software was specifically used to compare traffic operations at the intersections of Wanamaker Road and Huntoon Street (refer Figure 3) and Wannamaker Road and off-ramp of I-470 (refer Figure 3).
Figure 3. Wanamaker Road, Huntoon Street to I-470 Off-Ramp. (Source: Google Maps).
Vehicles that are exiting from I-470 via I-470 off-ramp and turning right (going North) onto Wanamaker Road experience many conflicts with north bound vehicles on Wanamaker Road. Similarly, left turning vehicles from the I-470 off-ramp face conflicts with south bound vehicles of Wanamaker Road. If we assume a roundabout replacing the existing signalized intersection at Wannamaker Road and Huntoon Street, then the left turns form I-470 off-ramp would make a right turn, travel north, make a U-turn at Wannamaker Road and Huntoon Street intersection and then proceed south on Wanamaker Road without facing severe conflicts.
Figures 4(a)-(d) indicates the hourly traffic volume of the intersections of Huntoon Street and I-470 ramp with Wannamaker Road before and after the assumed roundabout. The intersection of Wannamaker Road with Huntoon Street was initially signalized controlled; a roundabout control was assumed at this location. The Intersection of Wannamaker Road with I-470 off-ramp is T-intersection having stop control for I-470 off-ramp; for the after condition at this T-intersection, only right turns are allowed for vehicles from I-470 off-ramp and left turning vehicles should take a right turn, proceed to hypothetical roundabout at Wannamaker Road and Huntoon Street, take a U-turn and then proceed to their intended direction. At the Wannamaker Road and Huntoon Street intersection, traffic counts of approaching traffic and turning movements are same for the before and after situation (part A and part B of Figure 4), except for the south approach of Wannamaker Road in the after condition (refer part B of Figure 4) which has an additional 174 vehicles making U-turns; these 174 U-turns are vehicles that were making left turn from I-470 off-ramp onto Wanamaker Road at the T-intersection in the before situation (part C of Figure 4).
Figure 4. Hourly traffic counts of the intersections of Huntoon street and I-470 Off-Ramp with wannamaker road.
Based on SIDRA analysis, average delay per vehicle and level of service for each possible vehicle movement is calculated for all approaches of Wannamaker Road intersecting with Huntoon Street and I-470 off-ramp and is shown in Figure 5. It can be observed from Part B of Figure 5 that the delay on each movement is comparatively less for roundabout when compared to before treatment. The delay for left turns especially is observed significantly less; this trend is also observed for south leg of the Wannamaker Road and Huntoon Street roundabout even though the approach volume is 174 vehicles more. At signalized intersection, although vehicles travel faster while using the intersection when compared to roundabout, the wait time for a green light at signalized intersection reduces the overall average speed. An optimal cycle length of 108 seconds was used for the signalized intersection at Wannamaker Road and Huntoon Street intersection, and the SIDRA analysis showed that 20% of the left turning vehicles for the two approaches of Wannamaker Road cannot clear the intersection. Therefore, the left turn arrows (part A of Figure 5) for both approaches of Wannamaker Road are red indicating a level of service of “F”. Russell et al. have analyzed multiple roundabouts in Kansas and found that for any given level of traffic, various vehicle movements at roundabout generally operated at a minimum one level of service higher than comparable movements at signals  .
Total vehicle operating and time costs were analyzed for the current treatment of Huntoon Street and I-470 off-ramp with Wannamaker Road and compared to hypothetical roundabout treatment at Wannamaker Road and Huntoon Street. Classification of traffic vehicles was not available for intersections of Wannamaker Road with Huntoon Street and I-470 off-ramp, therefore SIDRA default values were used for a mix of different kinds of vehicles and percentage of trucks. The costs for all vehicle movements, except the left turn vehicle movements, are found substantially the same; for many instances, the costs for signalized options are slightly higher. The
Figure 5. Level of service and average delay for before and after roundabout treatment at Huntoon street and Wannamaker Road.
operating costs and time cost for left turning vehicles are found substantially higher for a signalized option mainly because of the delay experienced by left turning vehicles. Carbon-dioxide (CO2) emissions were found to be same whether the intersection is signalized treatment or a roundabout treatment. As far as emissions are concerned, through movements are slightly better with the signalized intersection and turning movements are slightly better with roundabout treatment. The additional right turn and the U-turn movements resulting by making Wannamaker Road and I-470 off-ramp intersection right turns only have generated additional CO2 emissions, however, they are considerably less when compared to emissions that are eliminated when the left turning vehicles at Wannamaker Road and I-470 off-ramp intersection are diverted toward the hypothetical Wannamaker Road and Huntoon Street Roundabout.
3.2. Business Entrance near the Bed Bath & Beyond Store
As a part of this study, one business entrance on Wannamaker corridor is also analyzed which is a T-intersection that provides access to a large parking lot that served several stores, including Bed Bath & Beyond and Hobby Lobby. This business entrance is shown in Figure 6.
Access onto Wannamaker Road from the business entrance is controlled by a stop sign. A signalized intersection is present immediately to the north of the T-intersection business entrance which serves IHOP and West Ridge Shopping Center on the west and K-Mart on the east. South of the T-intersection business entrance is another signalized intersection at 19th Terrace Road. For the purpose of after condition for this study, the two signalized intersections were replaced with hypothetical roundabouts and the left turns at the T-intersection were restricted. By restricting left turn movements at the business entrances, the left turn movements off of Wanamaker from the center lane are also eliminated. In this case, left turning vehicles onto the entrance off of Wanamaker and left turning vehicles onto the Wanamaker off of the entrance proceed to the roundabout just to the
Figure 6. Bed bath & beyond and hobby lobby access onto Wanamaker. (Source: Google Maps).
south and north roundabouts respectively and make a U-turn to continue their trip. A 16.4 second delay of left turning vehicles onto the entrance, a 474.8 second delay of left turning vehicles onto the Wanamaker off of the entrance has been eliminated after considering roundabouts. Moreover, the delay of right turning vehicles off of the entrance onto the Wanamaker has diminished from 42.4 seconds to 15 seconds.
3.3. VISSIM Analysis
Apart from the SIDRA analysis, a secondary analysis was conducted for the traffic in the vicinity of Wannamaker Road and Huntoon Street intersection using a different model―VISSIM. The objective is similar to that involved in the SIDRA analysis that was conducted at the selected intersection. Similar to SIDRA, VISSIM software is also used to analyze specific intersections, but can also be used to analyze a series of intersections or a limited network.
A VISSIM simulation was run for the current signalized configuration and the hypothetical roundabout configuration at Wannamaker Road and Huntoon Street and also for T-intersection (Wannamaker Road and I-470 off-ramp) south of the intersection which clearly showed that the queue length is much shorter on the I-470 off-ramp when all vehicles turn right and the southbound vehicles make a U-turn at the Wannamaker Road and Huntoon Street roundabout. The average delay and level of service results from the VISSIM analysis for the before after conditions at the two intersections of Wannamaker Road with Huntoon Street and I-470 off-ramp are summarized in Table 2. Average delay for all approaches at Wanamaker Road and Huntoon Street intersection is reduced from 32.8 seconds (signalized treatment) to 9.5 seconds (hypothetical roundabout treatment). The greatest reduction in the average delay for all the approaches is at T-intersection of Wannamaker Road and I-470 off-ramp from 92.9 seconds to 11.3 seconds. It has to be noted that some of the vehicles (174 vehicles) having a 11.3 second delay at the I-470 off-ramp terminal will also experiencing a 9.5 second delay while making a U-turn at Wannamaker Road and Huntoon Street roundabout. However, the total deal is still considerably less than what they are experiencing with the current configuration.
4. Conclusions and Recommendations
This study analyzed the impact of roundabouts at businesses to their business performance and overall traffic flow. This task is achieved by two major study objectives: 1) conducting survey of businesses around the roundabout corridors in different places in the US and 2) conducting a before-after study of a business corridor in Topeka, KS by simulating the after situation of the business corridor with a hypothetical roundabout treatment using SIDRA and VISSIM software.
An analysis of survey responses from business owners from Kansas and Indiana regarding the roundabout near their business has showed that business owners’ perception of roundabout differs with location of roundabout. Since roundabouts are relatively new in the United States, in some areas, their implementation tend to be a polarizing topic when they are initially introduced, i.e. strong supporters on one side and strong opponents on the other side. Similar results were also observed from the business owner surveys conducted in various cities in the state of Kansas and in Caramel, IN; business owner’s views vary from wide acceptance to non-acceptance. In Caramel, IN, 35.7% of the business owners felt roundabout was an “excellent” addition to their street or neighborhood, 35.7% felt “very good”, and 14.3% felt “good” i.e. a total of 85.7% of the respondents though that roundabouts have a positive impact on their business performance. Caramel, IN is relatively small to medium sized city with over 60 roundabouts and is called as “roundabout city”. In Topeka, KS 23.1% of the business owners felt roundabout was a “very good” addition to their street or neighborhood, and 38.4% felt “good” i.e. a total of 61.5% of the respondents though that roundabouts have a positive impact on their business performance. Roundabout acceptance seems to increase as the number of roundabout installations in an area increase and the
Table 2. Performance measures by VISSIM analysis.
length of time residents have been exposed to them. More public education about the safety effectiveness, performance metrics, and other advantages of roundabouts can probably increase their acceptance in the future. However, at present, as can be seen in the survey, views vary from wide acceptance to non-acceptance. The simulation of a hypothetical roundabout corridor on Wanamaker Road in Topeka, KS using SIDRA and VISSIM showed significant reductions in delay and queueing for most all significant traffic movements. The conclusion from the software simulations is that roundabouts installation would provide better traffic flow and improved access to businesses.
The funding for this study is provided by Kansas Department of Transportation.
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