Construction Project

Intersection Upgrades at SR-18 and Rimrock/Puite Roads

Project Manager: Justin Talago Project Engineer: Charles Belt Traffic Engineer: Dhyia Benosh


The system of intersections our consulting group studied for potential traffic upgrades is

located just east of the center of Apple Valley, CA along State Route 18 (SR-18). SR-18

in this area is a four lane divided highway that runs east-west and has two parallel two-

lane outer highways to the north and south. These two outer highways have existing

accesses to SR-18 at Rimrock Road to the north and Puite Road to the south. Our goal

in upgrading this system of intersections is to increase safety and increase circulation.

In order to achieve this we first propose to reconfigure the intersection geometrically

and then propose to upgrade the intersection with a well-timed signal that provides

minimum average delay. After reviewing several alternatives we propose eliminating

access to the main intersection from the outer highways, which will increase the queue

distance for Rimrock and Puite roads. The signal design we propose is a fully actuated

signal with three phases, allowing for the addition of protected left turns from SR-18.


Apple Valley is a small town located in the Victor Valley region of San Bernardino

County. The current population is close to 71,000, but the surrounding region has

upwards of 313,000 residents. The town of Apple Valley is currently interested in

attracting new businesses to boost it’s economy. With ambitious goals of growth the city

is looking into potential upgrades to their transportation systems. The main arterial

running east and west through Apple Valley is State Route 18 (SR-18). The stretch of

SR-18 that we are focused on has minimal access to the surrounding residential and

commercial areas. The intersection of Rimrock/Puite roads is particularly isolated with

the next closest intersection to the east being at Rancherias Road eight tenths of a mile

away, and Tao Road nine tenths of a mile to the west. It is also important to note that

there are several businesses to the east that create a high traffic demand along SR-18.

Figure 1: Overview of project area.

Project Overview:

(1) Site Selection

The intersection of Rimrock/Puite Roads and SR-18 is the site we focused our study on.

Our first observation of the site was that the distance between the outer highway

intersections and the main intersection was very short. This short length allows very

little queue distance for traffic entering SR-18 from the outer highways and

Rimrock/Puite Roads; the short queue length could potentially lead to traffic backing up

into the secondary intersections at the outer highways. Our second observation was

that the left turn pockets from SR-18 to Rimrock/Puite Roads were blocked, which

indicated that there were likely safety issues with the left turn movements from SR-18.

With the left turns being eliminated there is a side effect of decreasing the circulation at

the intersection.

(2) Initial Analysis

This system of intersections is currently controlled by stop signs for access to SR-18;

east-west SR-18 traffic and traffic exiting from SR-18 have no restrictions. The layout is

such that there is a stop sign controlled intersection to the north of SR-18 which

intersects the northern east-west outer highway and north-south Rimrock road (see

Figure 2). The stop signs at this outer highway intersection restrict traffic flowing from

three of the four directions, but do not restrict flows of exiting traffic from westbound SR-

18. The traffic flowing to westbound SR-18 from the stop sign controlled outer

intersection then has to continue south approximately 40 feet and queue at an

additional stop sign until it can safely continue onto westbound SR-18. The same layout

is mirrored on the south intersection of the outside highway and Puite Road.

The traffic volumes at the intersection were collected from Caltrans and the City of

Apple Valley. Because the data was not completely representative of the each individual

lane and direction, some data was estimated (see Appendix I for volume data).

Figure 2: a. Painted chevrons indicate that the left turn is off limits. b.The queue distance is only about 40 feet.

After our initial observations of the geometric layout, and analysis of traffic volumes we

determined that this site was an excellent candidate for study to come up with a safer

and more efficient intersection through geometric means and signalization.

(3) Geometric Redesign

The first issue with the geometry of the intersection system is that there are three

separate flows of traffic inbound from the north to the intersection to be signalized, as

well as three separate flows inbound from the south, which induces longer queues for

each flow. In order to decrease the queue we propose eliminating the stop sign

controlled intersections of this system all together. This can be accomplished by

physically restricting traffic from passing through the intersection from the westbound

and eastbound directions of the north and south outer highways. Those flows will

Figure 3: Traffic volumes for existing system of intersections at SR-18 and Rimrock/Puite Roads.

instead be rerouted to the south or north and then back east or west to Puite Road and

Rimrock Road. This will consolidate all traffic to two single flows; one from the north

along Rimrock Road, and one from the south along Puite Road.

By closing off the outer highways we will be restricting the flow of traffic in several

places. In order to accommodate traffic flowing from the outer highway to the north of

SR-18 we propose a new road connecting Rimrock Road with Rimrock Road East. We

also propose a new driveway to accommodate traffic to the Apple Valley Lodge.

We also propose opening up the left turn pocket from eastbound SR-18 to Rimrock

Road, and from westbound SR-18 and Puite Road. By opening up these left turn

pockets at the same time as closing traffic from flowing through the outer highways we

are simultaneously redirecting the circulation of traffic in some areas while introducing

new circulation in other areas. Because of high volumes, the introduction of left hand

turns presents an issue of safety, but we will address this issue through signalization.

Figure 4: a. Roadway removal. b. Knuckle turn for easy turning

maneuvers. c. Cul-de-sac for easy turnaround

maneuvers. d. Addition of a Serrano Rd to

connect Rimrock Rd E and Rimrock Rd.

e. Driveway added for lodge.

(4) Signal/Signage and Signal Design

In order to better optimize traffic flow, and to address some issues with our geometric

redesign, we also propose signal and signage changes. By eliminating the intersections

at the outer highways, we essentially propose eliminating one stop sign controlled

intersection to the north and one to the south. With the proposed construction of a road

connecting Rimrock Road East and Rimrock Road we also propose adding stop sign

controlled intersections at the junction of Rimrock Road and Serrano Road, and at

Rimrock Road East and Serrano Road.

With the circulation of traffic from the outer highways being redirected to the north and

south, we propose adding a signal to the main intersection of SR-18 and Rimrock/Puite

Roads. The signal will allow better circulation and increase the safety for approaches

from Rimrock and Puite Roads. The signal will also allow for protected left turns from

SR-18, which will improve circulation from SR-18 to the surrounding community.

For the proposed signal we looked at two different options. Our first option was to use a

semi-actuated signal in order to keep delays to a minimum by allowing only two phases.

Figure 5: a. Stop sign controlled intersection

added. b. Signalized intersection with

protected left turns from main highway

Because the left turn volumes from SR-18 are above the threshold required for a

protected left hand turn (see Figure 6), we were unable to propose the semi-actuated

signal. With the requirement of protected left turns we chose our second option, the fully

actuated signal type. Our assumptions can be seen in Figure 6, and calculations for the

signal timing can be found in the next section.

Figure 6: New intersection layout with traffic volumes and other parameters.

(5) Signal Timing

Using the parameters from Figure 6, and the formulas given in class our group went

through the process of computing the signal timing. See calculations below:

Step A: Signal Phase

Phase 1 (Ø1) : protected lest turn for EB/WB

Phase 2 (Ø2) :TH/RT for EB/WB

Phase 3 (Ø3) : simple phase signal for NB/SB

Step B: Passage time

PT = d / 1.47 * S��

PT = 3 ˃ 40 /1.47 * (45-5) = 0.68 Sec OK

PT = 3 ˃ 40 /1.47 * (35-5) = 0.9 Sec OK

Step C: Yellow , all red time and total lost time

Y = t + 1.47 * s��/2 * a + (64.4 * 0.01 * G)

Y (Ø1,Ø2) = 1 + 1.47 * (45+5)/20 = 4.67 Sec

Y(Ø3) = 1+ 1.47 * (35+5)/20 = 3.94 Sec

ar = W+L/1.47 * S��

ar(Ø1,Ø2) = (12 * 2) + 20 / 1.47 * (45 – 5) = 0.74 Sec

ar(Ø3) = (12 * 4) + 20 / 1.47 * (35 – 5) = 1.54 Sec

L = (0.74 + 4.67 )* 2 + 1.54 + 3.94 = 16.22 Sec

Step D: CLV

From table below: CLV = 363 + 501 + 295= 1159 (tuv/hr)

App. Mov. Volume (veh/hr)

Equ. Volume (veh/hr)

Lane group tvu/hr

Volume/Ln (tvu/hr/ln)


L 346 1.05 363 363 363

TH 900 1 900 941 471

R 35 1.18 41


L 206 1.05 216 216 216

TH 844 1 844 1002 501

R 134 1.18 158


L 33 1.33 44

251 251 TH 148 1 148

R 50 1.18 59


L 43 1.86 80

295 295 TH 139 1 139

R 64 1.18 76

Step E: Min green time and detector placement

G(min) = l1 + 2 * INT(d/25)

G(min) all = 2 + 2 * INT (40 / 25 ) = 6 Sec

Step F: Cycle length

C = L /{ 1- Vc / 1615 * PHF * (v / c )}

= 16.22 / (1 – 1159/ 1615 * 0.9 * 0.95 )

= 100.9 Sec

Step G: Max green time

G(tot) = C – L = 100.9– 16.22 = 84.68 Sec

G(Ø1) = 84.68 * 363 / 1159 *1.5 = 40 Sec OK

G(Ø2) = 84.68 * 501 /1159 * 1.5 = 55 Sec OK

G(Ø3) = 84.68 * 295/ 1159 *1.5 = 32 Sec OK

(6)Traffic Simulation:

In order to check our work and confirm that our signal and signal timing provide better

circulation and fewer delays than the existing stop sign controlled intersection we ran a

simulation using Corsim software. The data entries and model set up can be found in

the Appendix II. The delays can be found in the tables below.

Table 1: Current Intersection Layout

Delay Time (sec)

Delay Time (sec

Delay Time (sec

Delay Time (sec


L 1322.16


L 5005


L 1965.54


L 948.93

TH 1070.87 TH 2710.99 TH 108.18 TH 79.8

R 3944.5 R 2259.76 R 651.93 R 2498.09

Table 2: Proposed Intersection Layout with Fully Actuated Signal

Delay Time (sec)

Delay Time (sec

Delay Time (sec

Delay Time (sec


L 1373.6


L 115.65


L 562.12


L 196.46

TH 1067.04 TH 3184.76 TH 53.19 TH 29.33

R 47.95 R 245.12 R 184.45 R 534.64


After reviewing the layout and traffic volumes for the intersection at SR-18 and

Rimrock/Puite Roads, our consulting team determined that it was a good candidate for

geometric redesign and signal upgrades. With our proposed geometric reconfiguration,

and the placement of a well-timed signal we think that delays on this intersection can be

reduced dramatically. Table 1 above shows the delays seen at the intersection with its

current configuration, and when compared with Table 2 it is clearly shown that delays

can be reduced quite dramatically at some approaches.

Beyond the decrease in delays, our team feels that the new configuration for the

intersection will help improve circulation and safety in a major way. By removing the

outer highway to the north and south of the main intersection we are providing a safer

approach from the north and south of the main intersection. The addition of a protected

left turn should allow better and safer access to the surrounding residential and

commercial area from SR-18. In addition to making the intersection safer and more

traversable, removing access along the outer highways will force through traffic that

might be traveling to the businesses outlined in Figure 1 to stay on SR-18. Overall, we

believe the proposed upgrades will work well to help improve the traffic flow to the

growing town of Apple Valley.


Traffic volumes and data from Town of Apple Valley:

Traffic volumes and data from CALTRANS PEMS website:


Corsim network for existing condition:

Delay from Corsim for existing condition:

Corsim network for proposed upgrades:

Delay from Corsim for proposed upgrades:CIVE 580 Traffic Engineering Design

Course Group Assignment

Amin Shabihkhani, PhD, PE

Department of Civil, Construction

& Environmental Engineering

San Diego State University

Project Requirements

1. Group of 3 to 4-person team

2. Final presentation:

a. 10 – 15 min presentation and 5 min Q/A

b. All team members should present

c. Presentations will be scheduled for April 26th and May 3rd, 2018

3. Final project report

a. TRB format paper or report

b. min 8 pages typed single-spaced,

c. Draft report due April 19th

d. Final report due: May 3rd, 2018


Project Scoring

 Group Project : 25% of the course grade

 50/100 Presentation:

 10 – Overall evaluation (Classmates evaluation)

 10 – Presentation framework, (Slides, timing, intonation, etc.)

 15 – Content of the presentation

 15 – Delivery of message

 50/100 Project report:

 15 – Overall paper structure and content

 15 – Adequate literature review/problem statement

 20 – Satisfactory project discussion/problem solution


Project Topics

 Option 1 (Recommended):

Find your own topic

e.g., any transportation problem you can observe in your daily life (Scoping of project is required)


Project Topics

 Option 2: Select from the list

A. Research Topics: (1) Review paper (minimum 6 related papers)

(2) Research paper (I can help you with selecting a topic)

B. Design / applied projects (1) Signal Design for Conventional or Unconventional Intersections

(2) Rail Crossing Control System Design

(3) Ramp Metering System Design

(4) Variable Speed Limit System Design

(5) etc.


Standard Procedures

 Identify Problem

 Literature Review

 Methodology Development

 Application/Evaluation

 Conclusions


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