Bicycle Detection Using Caltrans Type D Loops:More Options for Practitioners

Presented toITE District 6 Annual Meeting

June 24-27, 2012by John Kerenyi, P.E., Senior Engineer,

City of Moreno Valley

Summary of Presentation

• California AB1581• Caltrans recommendations• Desired configurations/deviation from

Caltrans recommendations• ILD theory of operation• Type D loop field measurements• Calculations/recommendations

California AB1581

At new or substantially modified intersections (>50% of detection replaced), re: detection:“To the extent feasible and in conformance with professional traffic engineering practice, to be installed and maintained so as to detect lawful bicycle or motorcycle traffic on the roadway.”AB1581 became effective in 2010

Caltrans Guidance—Requirements• Reference rider described

– 4 ft tall– 90 lbs min– 16” aluminum wheels, non-ferromagnetic frame

• Reference rider described in a manner suitable for testing detection by many means e.g. ILD, video, microwave

• Either detect reference rider, or place approach on recall (semiactuated/pretimed operation allowed)

• Bike pushbuttons not enough anymore• Bike min green timing recommended

Caltrans Type D Loop

Type D Loop Variations

City of Moreno Valley

City of Los Angeles

Caltrans’ Type D Loop Recommendations

• Wire in series with three other standard (e.g. round or octagonal) loops which are connected in parallel to each other

• Wire in series with two other standard loops• Wire to own detector card channel

Detector Card

D

E E

Detector Card

D

E EEDetector

CardD

Desired Configurations

E D

E D

E D

E DE E

Case 1:Two loops in one lane

Case 3:Four loops in two lanes

Case 2:Four loops in one lane

ILD Theory of Operation

Sensitivity

Series or parallel?E D

E

DDcircuit

L

LSS

1

1

Parallel wiring

D

EDcircuit

LL

SS

1

1

Series wiring

DDetector

Card E

DDetector

Card

E

Seek to minimize

LD = 190 μH

LE = 60 μH(Three Turns)

(Five Turns)

Scircuit = 0.76 SD Scircuit = 0.24 SD

Sensitivityfactor

Case 1

L

LS

Case 2E DE E

E

DDcircuit

L

LSS

1

1

D

EDcircuit

LL

SS

1

1

Parallel wiring Series wiring

Maximize

Minimize

SD minimized by placing the Type E loops in series

SD minimized by placing the Type E loops in parallel

E

E

E

DDetector

Card

D

Detector Card

E E E

SF: 0.61(4 turns)

SF: 0.51(3 turns)

Case 3E D

E D

E

DD

Detector Card

EE

DDetector

Card

E

E

D

D

Detector Card

E

D

E

DDetector

CardE

D

Configuration 1 Configuration 2

Configuration 3 Configuration 4

SF: 0.33 SF: 0.17

SF: 0.26 SF: 0.17

Discrimination ofBicycles and Vehicles

• Desirable to avoid timing long minimum greens every cycle for occasional bicycles

• Known efforts– OCTEC ILD method

– Microwave: Intersector, others– Video detection manufacturers

Recommendations• Case 1 (two loops): Parallel

• Case 2 (one D and three E): Parallel/series (opposite ofCaltrans recommendation)

• Case 3

• Further research is necessary esp. for splashover

DDetector

Card E

E

E

E

DDetector

Card

E

DD

Detector Card

E