Alexander Dennis Limited Download PDF Report
Alexander Dennis Limited submitted a model Midi “MD35”, diesel-powered 33 seat (including the driver) 34-foot bus, for a 12 yr./500,000 mile STURAA test. Testing started on July 19, 2013 and was completed on May 2, 2014. The Check-In section of the report provides a description of the bus and specifies its major components.
The primary part of the test program is the Structural Durability Test, which also provides the information for the Maintainability and Reliability results. The Structural Durability Test was started on July 29, 2014 and was completed on April 18, 2014.
The interior of the bus is configured with seating for 33 passengers including the driver with six seats folding away for two wheelchair positions. Free floor space will accommodate 24 standing passengers resulting in a potential load of 57 persons. At 150 lbs per person, this load results in a measured gross vehicle weight of 28,210 lbs. The first segment of the Structural Durability Test was performed with the bus loaded to a GVW of 28,210 lbs. The middle segment was performed at a seated load weight of 24,650 lbs and the final segment was performed at a curb weight of 19,510 lbs. Durability driving resulted in unscheduled maintenance and failures that involved a variety of subsystems. A description of failures, and a complete and detailed listing of scheduled and unscheduled maintenance is provided in the Maintainability section of this report.
Effective January 1, 2010 the Federal Transit Administration determined that the total number of simulated passengers used for loading all test vehicles will be based on the full complement of seats and free-floor space available for standing passengers (150 lbs per passenger). The passenger loading used for dynamic testing will not be reduced in order to comply with Gross Axle Weight Ratings (GAWR’s) or the Gross Vehicle Weight Ratings (GVWR’s) declared by the manufacturer. Cases where the loading exceeds the GAWR and/or the GVWR will be noted accordingly. During the testing program, all test vehicles transported or operated over public roadways will be loaded to comply with the GAWR and GVWR specified by the manufacturer.
Accessibility, in general, was adequate, components covered in Section 1.3 (Repair and/or Replacement of Selected Subsystems) along with all other components encountered during testing, were found to be readily accessible and no restrictions were noted.
The Reliability section compiles failures that occurred during Structural Durability Testing. Breakdowns are classified according to subsystems. The data in this section are arranged so that those subsystems with more frequent problems are apparent. The problems are also listed by class as defined in Section 2. The test bus encountered no Class 1 or Class 2 failures. Of the 49 reported failures, 34 were Class 3 and 15 were Class 4.
The Safety Test, (a double-lane change, obstacle avoidance test) was safely performed in both right-hand and left-hand directions up to a maximum test speed of 45 mph. The performance of the bus is illustrated by a speed vs. time plot. Acceleration and gradeability test data are provided in Section 4, Performance. The average time to obtain 50 mph was 39.69 seconds. Top speed obtained on the dynamometer was 64 mph. The Stopping Distance phase of the Brake Test was completed with the following results; for the Uniform High Friction Test average stopping distances were 30.43’ at 20 mph, 56.45’ at 30 mph, 98.75’ at 40 mph and 139.00’ at 45 mph. The average stopping distance for the Uniform Low Friction Test was 34.92’. There was no deviation from the test lane during the performance of the Stopping Distance phase. Note; the ABS warning light came on several times throughout testing. The bus needed to be shut down each time to reset the ASB system. During the Stability phase of Brake Testing with the driver’s side of the bus on high friction surface the rear and right front brakes locked up. The bus veered left, then to the right and out of the lane. With the driver’s side of the bus on the low friction surface the rear and left front brakes locked up and the bus veered to the right and out of the lane. The Parking Brake phase was completed with the test bus maintaining the parked position for the full five minute period with no slip or roll observed in both the uphill and downhill positions.
The Shakedown Test produced a maximum final loaded deflection of 0.149 inches with a permanent set ranging between 0.000 to 0.004 inches under a distributed static load of 20,325 lbs. The Distortion Test was completed with all subsystems, doors and escape mechanisms operating properly. No water leakage was observed throughout the test. All subsystems operated properly.
The Static Towing Test was performed using a target load (towing force) of 23,412 lbs. All four front pulls were completed to the full test load with no damage or deformation observed. The Dynamic Towing Test was performed by means of a front-lift tow. The towing interface was accomplished using a hydraulic under-lift wrecker. The bus was towed without incident and no damage resulted from the test. The manufacturer does not recommend towing the bus from the rear, therefore, a rear test was not performed. The Jacking and Hoisting Tests were also performed without incident. The bus was found to be stable on the jack stands, and the minimum jacking clearance observed with a tire deflated was 2.8 inches.
A Fuel Economy Test was run on simulated central business district, arterial, and commuter courses. The results were 4.47 mpg, 5.32 mpg, and 9.23 mpg respectively; with an overall average of 5.54 mpg.
A series of Interior and Exterior Noise Tests was performed. These data are listed in Section 7.1 and 7.2 respectively.
The Emissions Test was performed. These results are available in Section 8 of this report.