Toledo Transit Authority Studies B20 Fuel Economy

After conducting a three-year fuel comparison study, the Toledo Area Regional Transit Authority compared two mechanically-identical Blue Bird buses operating on different fuels by alternating operation on the same duty cycle in transporting passengers. Overall, significant differences were found in their fuel economy.
By By David M. Nelson, Mark Vonderembse, S. Subba Rao and Mike Blackston | May 19, 2010
Nationwide transportation is at its highest level in 50 years. Currently there are 6,400 providers of public transportation in the U.S. Many of these transportation providers are seeking to help reduce the nation's reliance on foreign oil by incorporating alternative fuels such as biodiesel. U.S. public transportation ridership has increased significantly within the past few decades. According to the American Public Transportation Association, public transportation ridership increased 168 percent between 1970 and 2007. During this same period, the U.S. population has increased by 48 percent (Figure 1).

Reduction of dependency on foreign oil is not the only reason for seeking alternative fuels such as biodiesel. There are other advantages, such as the reduction of environmental degradation and pollution. Many major cities are now seeking new and emerging technologies, such as hybrid-electric vehicles, biofuels and other clean-energy alternatives. Transit authorities generally agree that addressing global warming requires taking a broader perspective of these issues.

Mass transportation offers a good investment. According to APTA, activity over the next 10 years focusing on reshaping transportation infrastructure can benefit the local economy. Using public transport not only makes economic sense, but it is also beneficial for the environment. Due to rising fuel prices, more Americans are using public transportation because it offers an affordable and efficient mode for shopping, going to social events, school and work.

The fleet of the Toledo Area Regional Transit Authority consists of 194 vehicles dedicated to public transportation, with 140 buses for regular transit, six smaller vehicles offering on-call service, and 48 buses for paratransit assistance.

Ridership on TARTA experienced an increase between 2007 and 2008, with a total volume of 4.7 million passengers in 2008. Like other mass transportation authorities, TARTA has pursued the use of alternative fuels. In 2006, a three-year study commenced with the use of biodiesel, based on a B20 blend of soy biodiesel and ultra-low sulfur diesel (ULSD). During the study, 116 of the diesel-powered buses, 60 percent of the TARTA fleet, were converted to B20 fuel. The fleet experienced a variety of operating conditions ranging from optimal, warm summer weather, to suboptimal, freezing winter conditions typical in the Midwest.

During the three-year study, it was observed that using biodiesel fuel sometimes achieved lower fuel economy than buses operating on conventional diesel. Over the course of the study, two types of routes were typically utilized: stop/go and express travel. Since buses were driven on ULSD and B20 during these travel routes, it was decided to perform an exploratory investigation to see if there was any difference between fuel use and travel route. Two mechanically-identical Blue Bird buses operating on different fuels were subsequently compared by alternating operation on the same duty cycle in transporting passengers. The current exploratory study took place during the optimal operating months of July and August 2009.


Research Scope

During the TARTA biodiesel study, it was discovered that buses running on conventional diesel periodically achieved better mileage than those driven with B20 fuel. This, however, conflicts with other work, but no investigation took place regarding whether the same result occurs while operating in different travel routes, such as stop/go and express driving. Since biodiesel offers several emission advantages over conventional diesel, it was decided to investigate whether there are any other benefits in the two routes of travel.

Maintenance records in the TARTA fleet were investigated, and two Blue Bird buses were selected for this study. The routes chosen were representative of those typically driven by buses in the fleet. The buses chosen operated during a two-week period under optimal climate conditions beginning in late July 2009. When the study was completed, both the express and stop/go driving results were statistically compared. Mileage driven and fuel consumed per day were the test parameters used in the study.


Methodology and Results

Initially, a meeting was set up with TARTA's director of information services to establish the logistics and protocol for the study, including route selections, driver assignment and field data collection. During the study, data consisted of daily mileage driven and fuel consumption. All four data sets-two for B20 (express and stop/go), and two for ULSD (express and stop/go)-were explored with general statistics and analyzed with a two-way Analysis of Variance (ANOVA).

Five days of usage were analyzed for each type of fuel (ULSD and B20), with each of the two travel modes. A total of 1,397.7 miles were driven with Bus 301 using B20. Express mode resulted in 658.7 miles traveled. Stop/go reflected 739 miles.
The bus operating on ULSD was driven a total of 1,892.8 miles. Stop/go reflected 1,036.8 miles, while express accounted for 856 miles.

The results were inconsistent with the conclusions found previously in TARTA's three-year study. For the current exploratory study, the statistical results with two-way ANOVA indicated there was a significant difference when reflecting on B20 fuel or ULSD fuel at the P<.05 level, but not in the travel type of express or stop/go travel for bus use in the study.


Conclusions

This investigation seems to conflict with previous work where there was no significance noted in the test results between two groups of buses operating on B20 and conventional diesel over a three-year period. In the current short-term study there was also no significance noted for one of the parameters. However, the statistical analysis showed significance for both fuel type and interaction, which indicates that a difference does indeed exist. Additionally, when reflecting on the average miles-per-gallon graph for both fuel types and operating conditions, the vehicle operating on ULSD achieved better fuel economy in stop/go traffic than in the express mode, while the bus operating on B20 performed better in express traffic conditions than in the stop/go mode. When all four of these parameters are taken into consideration, there is a possibility that the fuel type could, however, influence the MPG when considering both stop/go and express travel. Graphical results support this.

The average values of fuel economy comparison between the two vehicles are graphed and exhibited in Figure 2. Even though the bus using B20 exhibited an improvement as it shifted from traveling in the stop/go mode to an express one, this did not occur with the vehicle using ULSD fuel. For the vehicle using ULSD fuel, stop/go travel achieved better MPG than in the travel mode. Additionally, the MPG of the ULSD vehicle was found to be better than the biodiesel vehicle in stop/go mode.


Recommendations

Previously it was shown that decreasing ambient temperature can adversely affect biodiesel use, such as the extreme cold weather conditions found in the Midwestern U.S. It was also found by other authors that there is no significant difference between use of B20 and conventional diesel in a longitudinal study. No interaction was investigated by them, however, and this study seems to conflict with their results, offering potential insight for future investigation of fuel economy.

Further study aspects could entail the following:

1. TARTA could apply these preliminary findings to assist in making funding decisions, and possible grant application pursuit for more longitudinal studies to better depict whether there is a difference between stop/go and express travel in vehicles operating on biodiesel versus pure diesel.

2. A longer-term study could be performed with more vehicles to provide more insight into whether there is a difference between stop/go and express travel in various blends of biodiesel versus pure diesel.

3. It may be beneficial to incorporate all direct/indirect costs into a similar study related to each vehicle, such as maintenance (planned, and unscheduled), fuel, and other attributable overhead.


David M. Nelson is with the college of business at University of Toledo. Reach him at Nels.4@comcast.net. Mark Vonderembse is director of the Intermodal Transportation Institute at UT. S. Subba Rao is with the department of Information Operations and Technology Management at UT. Mike Blackston is with Toledo Area Regional Transit Authority. Reach him at mblackston@tarta.com.
 
 
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