CVE 442 Midterm

8/9/2019 CVE 442 Midterm

1/23

2014

Juan Villa

CVE 442

11/4/2014

CVE 442: Midterm Exam


2/23

CVE 442-Midterm Exam

I. Proof of Assimilation of Concepts(15 pts)

Define the duties of a traffic engineer !1 pt"Transportation engineering is the application of technology and scientific principles to the

planning, functional design, operation, and management of facilities for any mode of

transportation in order to provide for the safe, rapid, comfortable, convenient, economical, and

environmentally compatible movement of people and goods.Traffic engineering also is that phase

of transportation engineering which deals with the planning, geometric design and traffic

operations of roads, streets, and highways, their networks, terminals, abutting lands, and

relationships with other modes of transportation

The duties of a generic traffic engineering are mainly thought of as an intergration of the

conepts and theories of Civil engineering and modofyign those learnings into a traffic

engineering scale. Therefore, some of the usual jobs include planning, geometric design,

and operation of roadways, their networks, terminals, abutting land, and relationshipwith other transportation modes in order to provide for the safe, rapid, comfortable,

convenient, economical and environmentally compatible movement of people and goods.

Descri#e the $igh%a& Capacit& Manual's method for assessing the capacit& and

the (ualit& of flo% at a free%a& !2 pts"

Capacity

The HCM defines capacity as; "The maximum sustainable flow rate at which vehicles

or persons reasonably can be expected to traverse a point or uniform segment of alane or roadway during a specified time period under given roadway, geometric,traffic, environmental, and control conditions"The HCM capacity for each facility

type is computed according to the equations below.

The following equation is used to compute the capacity of all uninterrupted flow

facilities (freeways, multilane highways, and twolane rural roads!

Cap # $ase Cap % & % fh'% H)% fp% fg*Equation 3+

here

Cap # Capacity in terms of 'ehicles per hour.

$ase Cap # $ase capacity in terms of passenger cars per hour per lane

('aries by facility type!.

& # &umber of through lanes.

fh'# Hea'y 'ehicle ad-ustment factor ('aries by facility type, 'ehicle mi, and

grade!.

H) # ea/hour factor (the ratio of the pea/ 01minute flow rate to the

a'erage hourly flow rate!.


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fp# 2ri'er population ad-ustment factor (used for freeway and multilane

only!.

fg# 3d-ustment factor for grades (used for twolane highways only!.

)or freeway and highway wea'ing sections the capacity is a function of wea'ing type,

number of lanes, freeflows speed, length and wea'ing ratio. 2ue to thediscontinuous nature of the procedure for wea'ing sections, no closed form equation

for capacity is a'ailable.

The following equation is used to compute the lane group capacity for an approach to

a signali4ed intersection

s # (g5C! so& fwfH6fgfpfbbfaf78f7Tf9Tf7pbf9pb*Equation 4+

here

cap # Capacity for sub-ect lane group, epressed as a total for all lanes in

lane group ('eh5h!.

g5C # :ffecti'e green time per cycle ratio for lane group.

so# $ase saturation flow rate per lane (pc5h5ln!.

& # &umber of lanes in lane group.

fw# 3d-ustment factor for lane width.

fH6# 3d-ustment factor for hea'y 'ehicles in traffic stream.

fg# 3d-ustment factor for approach grade.

fp# 3d-ustment factor for eistence of a par/ing lane and par/ing acti'ity

ad-acent to lane group.

fbb# 3d-ustment factor for bloc/ing effect of local buses that stop within

intersection area.

fa# 3d-ustment factor for area type.

f78# 3d-ustment factor for lane utili4ation.

f7T# 3d-ustment factor for left turns in lane group.

f9T# 3d-ustment factor for right turns in lane group.

f7pb# edestrian ad-ustment factor for leftturn mo'ements.

f9pb# edestrianbicycle ad-ustment factor for rightturn mo'ements.

The following equation is used to compute the lane group capacity for the approach

to a roundabout and for a stop sign controlled approach to an intersection

*Equation 5+

here

cp,# otential capacity of minor mo'ement ('eh5h!.

'c,# Conflicting flow rate for mo'ement ('eh5h!.


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tc,# Critical gap (s!.

tf,# )ollowup time for minor mo'ement (s!.

the Highway Capacity anual!s method for assessing the capacity and the "uality of flow

at a freeway pedends on various measures. The first set of measures includes the measureof the freeway!s performance. eaning, how well does the freeway perform whencompared to other standard freeways# $ome of the performance measures include its

safety, capapcity, lane width, velocity, clealarce, number of lanes, level of service,

vechicle demands per unit of time and flow patterns

)ualit& of *lo%

%evel of service (%&$) is a "uality measure describing operational conditions within a

traffic stream, generally in terms of such service measures as speed and travel time,

freedom to maneuver, traffic interruptions, comfort and convenience.' (HC , pg.*).

A letter designation+ A through *+ that descri#es a range of operating

conditions on a particular t&pe of facilit& ,eel of serice A represents the

#est leel of serice and descri#es free flo% operations and er& lo% dela&s

,eel of serice * represents the %orst operating conditions

The HC has a method for assessing the "uality of flow at a freeway. This is done so bydetermining the ,eel of .erice of such freeway. The steps for calculating the %&$ are

shown below+

.tep 1 Compute the free flo% speed

here+FFS- free flow speed,

BFFS- base free flow speed ( mph, default),

.tep 2 Compute the flo% rate

here+fLW- adjustment for lane width,fLC- adjustment for lateral clearance,

fM- adjustment for median type,

fA- adjustment for access point density.

AMLCLW ffffBFFSFFS =

)/()/(//

))()()((

++

=

=

RRTT

HV

HVp

p

EPEPf

ffNPHF

Vv


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.tep / Construct a speed flo% cure for the facilit& using free flo% speed

interpolations

.tep 4 Determine the aerage passenger car speed+ S+ associated %ith the flo% rate

computed in .tep 2 gien the cure constructed in .tep /

.tep 5 Compute the densit&

.tep 0 se ta#le to assess the leel of serice associated %ith preious densit&

S

vD p=


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Descri#e ho% to modif& the preious method to guide the design of a free%a& or

multilane high%a& !2 pts"

There are three types of analysis that can be conducted for basic freeway sections and multilanehighways

0n addition, the HC defines .planning analysis.' This,however, consists ofbeginning theanalysis with an 112T as a demand input, rather than a peak hour volume. 3lanning analysis

begins with a conversion of an112T to a directional design hour volume (22H4).

5ou could modify the previous method to guide the design of a freeway by adjustingvarious factors that modifify the HC method+

6actors+

1djustment for lateral clearance1ccess*3oint 2ensity7 1djustment

1djustment for median type

1djustment for lane width


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0n order for a traffic engineer to modify the previous method to guide the design of afreeway or multilane highway they must take into consideration various factors. These

include some of the Human89ser $ensory Capacities like visuals, kinesthetic abilities,

vestibular abilities, and 1uditory $timuli83erception of the people driving on the road.Having these concepts can help modified the previous method.

3h& does the configuration of a %eaing section impact on its leel of serice and

capacit& !1 pt"

eaving areas (weaving occurs when one movement must cross the path of another along

a length of facility without the aid of signals of other control devices)

weaving area (area within on*ramp and off*ramp separated by less than , or : ft)

weaving flow (the two flows that cross each other at weaving areas)


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;

. pc8mi8ln for freeways

or =. pc8mi8ln for multilane highways.


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The configuration of a weaving section impacts the level of service and capacity because

the as a driver, it is important that the driver has as much time to maneuver around a

given section for safety reasons. Therefore, the weaving of the segment will make iteasier or harder for the driver to relocate on the road. $o for e?ample, if the weaving of

the section makes it harder for the driver to maneuver on the road, the less conficence he

has in driving and therefore the slower he will drive and this decreases the capacity of theroad because now youre affecting the flow of traffic.

3h& is concentration the measure of choice for assessing the leel of serice of

free%a& facilities 3h& not use speed instead !1 pt"

The use of density, rather than speed, is based primarily on the shape of the speed*flow

relationships depicted in 6igures /.> and /.=. @ecause average speed remains constant throughmost of the range of flows and because the total difference between free*flow speed and the speed

at capacity is relatively small, defining five level*of*service boundaries based on this parameter

would be very difficult


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The intention of %&$ is to relate the traffic service "uality to a given flow rate

of traffic

2ensity gives the pro?imity of other

vehicles in the stream. $ince it affects the ability of drivers to maneuver in the traffic

streamconcentration the measure of choice for assessing the level of service of freeway facilities

because speed is just a measure of how fast a vehicle is displacing from point a to point b

without any other measurement that could help us estimate a %&$. @ut when usingconcentration, we can get a better feeling as to how well the road is behaving because

conetration is a measure of the number of vehicles per unit length

3hat is the expression of the directional design hourl& olume in terms of

aerage annual dail& traffic on an ur#an radial facilit& !1 pt"

the e?pression of the directional design hourly volume in terms of average annual dailytraffic on an urban radial facility is+

DAAD6 7 DD$V


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8ased on &our reie% of the generic dail& and monthl& factors+ %hat da&!s" of

the %ee9 and month!s" of the &ear are prefera#le for executing traffic counts and

assessing the directional dail& traffic %ithout dail& or seasonal ad:ustments !1

pt"

The day(s) of the week and month(s) of the year are preferable for e?ecuting traffic

counts and assessing the directional daily traffic without daily or seasonal adjustments isproblably going to be the months of spring and fall which would include Aovemeber B

&ctober as well as ay B 1pril. 0 think these are probable months because their monthly

factors are the best fir for a range close to /. 1s far as the days are concern, 0 would say

that the first and the last days of the week are probably the best days to pick. These dayswould include onday and Tuesday as well as Thursday and 6riday. 0 pick these factors,

because, just as the factors for the months selected, for the days chosen the factors are

closer to /.

3hich leel of serice %ould &ou target for facilit& design in the &ears E6C and

E6C;2


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The ma?imum hourly rate at which persons8vehciles can e?pect to tracerse a point of

lane8roadway in a given time period under prevailing traffic8roadway conditions

Define serice flo% rate !1 pt"

The e?pected rate of flow on a roadway under given traffic conditions and control

conditions while sustaining a particular %&$

Derie the hea& ehicle e(uialent !1 pt"

fHV=

heavy-vehicle adjustment factorET =passenger-car equivalents for trucks and/or buses

ER= passenger-car equivalents for recreational vehicles

PT, PR=proportion of trucks or buses and RVs in the traffic stream

Explain the difference #et%een serice and maximum serice flo% rates !1 pt"

the difference between service and ma?imum service flow rates is that the service flowrate is the e?pected rate of flow on a roadway under given traffic conditions and control

conditions while sustaining a particular %&$, meanwhile

that for the serice flow rates the flow rate that is already e?pected under given onditions.

6or e?ample, on weekdays in the morings and in the afternoons you can e?pect flow rates

to be very low becoase eve everyone in either coming from or going to and from work.&n a ma?imum service flow rate, it only measures the ma?imum flow rate on a given

road, regardless of what you e?pect, it is the measurement of the ma?imum flow rate on

the road. $ee, $ervice flow rates are stated in terms of peak flows within the peak hour, usuallyfor a /:*minute analysis period, meanwhile ma?imum service flow rates depend upon the free*

flow speed of the facility.


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II. Compute the a=imuths of all lines of a closed traerse EA8CDE %hose #alanced

angles to the right !5 in total" &ou %ould hae chosen !Please use at the er& least

three dissimilar angles" Also select the a=imuth of an& course of the traerse asstarting point for &our anal&sis !5 pts"


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>>>

>V Design a sag ertical cure for a road%a& segment under construction Choose

the #ac9%ard and for%ard tangent grades %ithin the range of -2? and 5? !Please

select t%o une(ual alues %ithin the gien range" !5 pts"

.tation Distance

from

8VC

6angent

Eleation

@ffset Eleation

=D/>E >:.=> >:.=>

=D >=.: .// >=./

=D> / >> .D >>.D

=D= >/.: /.F >>.=

=D: > > >. >>=D = FE.: :.F >=.=

=DD : FD E.D >:.D

=DE F:.: /.// >D./

=DE D= F=.:D /=.=E >F.:


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V. Design a simple hori=ontal cure to connect t%o road%a& tangents that deflect at

an angle chosen #et%een 5< and 5 degrees Choose a left deflection angle Assign a

station to the cure P> and select a degree of cure #et%een / and 0 degrees Choose

coordinates for the point of tangenc& and an a=imuth for the for%ard tangent

Proide the cure data including the deflection angles from the tangent at the point

of cure to full stations on the cure+ the chords to preious stations and the

coordinates of fullstations(/ pts).

$tation 2eflection1ngle

Chord%ength

3C F=> />>.:

. .

F==t /. .F


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F=: =. /.

F= .= /.

F=D E.E /.

F=E //./ /.

F=F />.: /.

F: /:.F /.F:/ /E.> /.

F: .D /.

F:> >./ /.

3T F:>>E.>: =. >E.=


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.tation Distance

from

8VC

6angent

Eleation

@ffset Eleation

=D/>E >:.=> >:.=>

=D >=.: .// >=./=D> / >> .D >>.D

=D= >/.: /.F >>.=

=D: > > >. >>

=D = FE.: :.F >=.=

=DD : FD E.D >:.D

=DE F:.: /.// >D./

=DE D= F=.:D /=.=E >F.:


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.tation Deflection Angle Chord ,ength Coordinates

3C F=> />>.: . . :G =E ' A

F==t /. .F :G =E ::' A

F=: =. /. ::G > ' AF= .= /. :>G / >E' A

F=D E.E /. :G := ' A

F=E //./ /. :/G E =:' A

F=F />.: /. =FG => =>' A

F: /:.F /. =DG >/ >:' A

F:/ /E.> /. =G :' A

F: .D /. =>G = =' A

F:> >./ /. =G :/ E' A

3T F:>>E.>: =. >E.= =G / ' A

CVE 442 Midterm

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