CE 361 Introduction to Transportation Engineering
Test 3 (6 questions on 6 pages)
OPEN BOOK AND NOTES
Name: _____jdf Solutions_________
3:20-4:50 PM, Wed. 12 December 2007
Room 261 ME
For each question, show enough of your work or provide sufficient explanation to allow the
grader to follow your solution process and, in the case of an incorrect answer, award partial
credit. “FTE” = CE361 textbook.
1. ESALs for pavement design. An alternative to the standard 3-S2 axle configuration (see
FTE Figure 9.7) is replacing the rearmost tandem axle with two single axles about ten feet
apart.
A. (5 points) Would the new axle configuration still be given as 3-S2? If not, what is its new
designation?
B. (10 points) If the load supported by the rearmost tandem axle in FTE Figure 9.7 is now
shared by the two new single axles, what is the impact (in ESALs) that the truck would
have on the pavement?
A. Yes. It is still a semi-trailer with 2 axles, whether tandem or 2 x
single.
(0:40)
4
4
 Wsin gle   32,000 / 2 
 =
B. (9.1) ESAL = 
 = 0.624 each axle.
 18,000   18,000 
2 x 0.624 = 1.248 ESALs (versus 0.86 for tandem axle)
(2:23)
CE361 Test 3
-2-
Student initials: ___jdf___
2. (15 points) Public Mass Transportation. The Mythaca Bus Company wants to buy new
buses to serve the increasingly popular route that connects the central campus with a
remote student parking lot near the football stadium near the edge of campus. The MBC
staff is considering three bus types: the standard 40-seat bus with diesel engine, a 40-seat
hybrid electric-diesel bus, and a 60-seat articulated bus with diesel engine.
The 2.6-mile Campus-Stadium Loop takes 15 minutes to complete (including a 2-minute
break at the remote lot end). Assume headways of 7.5 minutes for the 40-seat buses and
15 minutes for the artic. Complete the entries in the cost analysis table below for the first
year of service on the Campus-Stadium Loop. In your calculations, use $3.20/gal, 12 hrs of
service per day, 300 days per year, $29.40/hr/driver. Show calculations below.
40-seat standard 40-seat hybrid
60-seat articulated
Campus-Stadium Loop
buses
buses
buses
Buses/hr needed
2
2
1
Purchase price per bus
$285,000
$465,000
$715,000
st
Total depreciation cost, 1 year
$95,000
$155,000
$119,167
Fuel economy
Total fuel cost per year
Total driver costs
Maintenance 1st year, each bus
3.9 mpg
5.7 mpg
3.4 mpg
$61,440
$211,680
2*$6693
$42,037
$211,680
2*$8345
$35,238
$105,840
$381,506
$425,407
Depreciation calcs. (FTE p. 542):
($285,000/12)*2 = $47,500 * 2 buses = $95,000;
($465,000/12)*2 = $77,500 * 2 buses = $155,000;
($715,000/12)*2 = $119,667.
Fuel cost calcs:
Total 1st year cost of service
2.6 mi 8 loops 12 hrs 300 days gal $3.20
*
*
*
*
*
loop
hr
day
yr
3.9 mi
gal
=$61,440/yr
2.6 mi 8 loops 12 hrs 300 days gal $3.20
*
*
*
*
*
loop
hr
day
yr
5.7 mi
gal
= $42,037
$7940
$268,185
2.6mi 4 loops 12hrs 300days gal $3.20
*
*
*
*
*
= $35,238
loop
hr
day
yr
3.4mi gal
Driver cost calcs:
2 drivers 12 hrs 300 days $29 .40
*
*
*
hr
day
yr
driver
= $211,680
1 driver 12 hrs 300 days $29 .40
*
*
*
=
hr
day
yr
driver
$105,840
Maintenance costs: $6693 * 2 buses = $13,386
$8345 * 2 buses = $16,690
(13:04)
CE361 Test 3
-3-
Student initials: ___jdf___
3. Airport operations and design.
A. (5 points) If a particular aircraft is a member of aircraft approach category C, what is its
minimum landing speed?
B. (7 points) If the FAA changes the assumed average weight of passenger + luggage
from 90 Kg to 100 Kg, what would be the new solution for Case 3 in FTE Table 11.24?
C. (8 points) Runways 28L and 28R are each 6240 feet long and are 1219 feet apart. If
their aircraft mix is 18% A, 27% B, 38% C, and 17% D, what ASV value should be used?
What is the maximum number of operations to allow, so that average delay will not
exceed 1 minute per aircraft?
A. FTE Index  Chap 11 Glossary p. 633: 121-141 knots
B. In Case 3, 57,289 lbs remaining for payload and fuel.
Subtract 81 pax *100 Kg/pax * 2.2046 lb/Kg = 17,857 lbs
57,289 – 17,857 = 39,432 lbs for non-reserve fuel.
39,432 lbs/22 lbs per mi = 1792 mi.
(14:00)
(16:00)
C. MI = 38 + (3*17) = 89
Parallel runways 1219 feet apart fall into Runway configuration No. 2 in
FTE Figure 11.23. ASV = 285,000 ops/yr for that MI value.
FTE Figure 11.24: 1 minute per aircraft average delay  DF = 0.85.
(11.9)’ Annual demand = 0.85 * 285,000 = 228,000 ops/year
(18:18)
CE361 Test 3
-4-
Student initials: ___jdf___
4. Moving freight.
A. (5 points) By rail. A new railroad line is being designed. The worst horizontal curve
along the proposed route has a 9.4 degree of curvature. Elsewhere along the route, a
change in elevation will determine the ruling grade. What is the maximum grade G that will
not cause resistance that exceeds the resistance caused by the horizontal curve?
B. (15 points) By tow. Which tow will generate more resistance to be overcome – a 3x2
tow or a 2x3 tow? Explain. Assume that the Froude number will be less than 0.15 in both
cases. Other information, if you need it: 8-foot draft and speed = 4.3 knots.
A. (12.7) Rcurv = 0.8 * 9.4 = 7.52 lbs/ton.
(12.6)’ G = Rgrade/20 = 7.52/20 = 0.376 percent grade.
(20:00)
B. Fr<0.15, so Rtot = Rsf.
(12.15) f3x2 = 0.0106*L-0.031 = 0.0106*((2*195)-0.031) = 0.00881
f2x3 = 0.0106*((3*195)-0.031) = 0.00870
Perimeter3x2 = (6*35)+(4*195) = 990 ft * 8-ft draft = 7920 sq ft
wetted sides.
Perimeter2x3 = (4*35)+(6*195) = 1310 ft * 8-ft draft = 10,480 sq ft
wetted sides.
Bottomboth = 35*195*6 = 40,950 sq ft
Swet for 3x2 = 7920 + 40,950 = 48,870 sq ft
Swet for 2x3 = 10,480 + 40,950 = 51,430 sq ft
Use (12.14) without the V term to save time.
For 3x2 tow: Rsf = 0.00881*48,870 = 430.55*V1.825
For 2x3 tow: Rsf = 0.00870*51,430 = 447.44*V1.825
[With the V term, Rsf = 6167 lbf for 3x2, and Rsf = 6409 lbf for 2x3.]
The 2x3 tow causes more resistance than the 3x2 tow.
(28:30)
CE361 Test 3
-5-
Student initials: ___jdf___
5. Energy, environment, technology, and sustainability.
A. (5 points) CAFE standards. Even if the mpg standard for new cars sold is raised and
benchmarks are put into place for intermediate years, what about the way vehicles are
purchased in the US will postpone the full impact of the new standards in the US
automobile fleet mix?
B. (5 points) At what constant speed are the NOx emissions from automobiles minimized?
A. Most cars in the fleet are more than one year old. Not all cars are
bought new; many are bought as used cars. So most of fleet will not
meet new CAFE standards. Must wait for older cars to be scrapped.
(30:00)
B. See FTE Figure 13.9. Min NOX at 20 mph.
(31:00)
CE361 Test 3
-6-
Student initials: ___jdf___
6. (5 points each item) Meet Mythaca’s Mayor! Later this evening, you will find yourself at the
annual Christmas/holiday reception sponsored by the Mythaca Chapter of the Institute of
Transportation Engineers. As usual, the Mayor of Mythaca and the City Engineer will be
there. The mayor loves to learn about the fields in which other people work, so she will
certainly ask you questions about transportation engineering. If she asks you the questions
listed below, you should be able to answer them without consulting any reference material.
(In other words, don't embarrass yourself in front of the City Engineer by going out to the
parking lot to get your CE361 materials from your SUV.) Keep your answers as brief as
possible. I'll assume that you can continue your conversation with the mayor after you give
the brief initial answer that you write below.
A. Why does a pothole keep forming near the gutter across the street from the old campus
Field House?
B. When Mythaca Bus Company gets its first hybrid bus, should they put it into service on a
downtown route or on a more rural route? Why?
C. The MYH airport director said that the main runway’s length was designed for an air
temperature of 80 degrees. Does that design also apply when temperatures are hotter
than 80 degrees?
D. The City Engineer tells me that there are two technologies that can be used by a transit
bus to pre-empt a traffic signal. Describe one of the two.
A. No catch basin at low spot. Water stands and gets under pavement
surface.
B. Hybrids have their greatest advantage over conventional internal
combustion engines when stops are frequent. Downtown operation
makes the most sense.
C. No, higher temperatures require a longer runway.
D. Either (a) loops in the pavement detect and identify an approaching
bus and “notify” the signal controller to prolong the green phase or (b)
an emitter on the approaching bus sends a “message” to a sensor on the
traffic signal to prolong the green phase.
(36:30)