Download presentation

Presentation is loading. Please wait.

Published byMargaret Chase Modified over 2 years ago

1
Traffic Flow Characteristics (2)

2
Learning Objectives To differentiate between interrupted and uninterrupted flow facilities To define general and linear speed-density relationships To derive, sketch, and apply Greenshield’s Model of traffic flow

3
Recap Spacing

4
Recap Clearance

5
Recap Density # vehicles/Distance

6
Recap… Speed (v) – ft/sec or mph Flow (q) – veh/sec or vph Density (k) – veh/ft or vpm Spacing (s) – ft/veh Headway (h) – sec/veh Clearance (c) – ft/veh Gap (g) – sec/veh Remember, units are critical!

7
Fundamental Relationships q = k v (veh/hr) = (veh/mi) (mi/hr) h = 1 / q (sec/veh) = 1 / (veh/hr) (3600) s = 1 / k (ft/veh) = 1 / (veh/mi) (5280)

8
Types of Facilities Uninterrupted flow –Freeways –Multilane highways –Two-lane highways

9
Types of Facilities Interrupted flow –Signalized streets –Un-signalized streets with stop signs –Transit lanes –Pedestrian walkways

10
General Speed-Density Relationship Free V K Jam Density Density at Capacity S Q Traffic Jam Capacity normal flow forced flow p.130

11
General Speed-Density Relationship Free V K Jam Density Density at Capacity K Q Traffic Jam Capacity normal flow forced flow p.137

12
General Speed-Density Relationship Free V K Jam Density Density at Capacity Q V Traffic Jam Capacity p.137

13
Greenshield’s Model Assume a linear relationship between v and k: High Density = Low Speed Low Density = High Speed vfvf kjkj

14
Greenshield’s Model K Q Max flow q max K0K0 KjKj vfvf v0v0

15
Greenshield’s Model Q V Max flow Q max VfVf V0V0 1/k 0 =s 0

16
Example Assuming a linear v-k relationship, the mean free speed is 60 mph near zero density, and the corresponding jam density is 140 vpm. Assume the average length of vehicles is 20 ft. Find: –v(k) and q(k) –Sketch v-k, v-q, and q-k diagrams –Compute v and k at q=1000 vph –Compute the average headway, spacings, clearances, and gaps when the flow is maximum

Similar presentations

Presentation is loading. Please wait....

OK

Traffic Flow Fundamentals

Traffic Flow Fundamentals

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on chapter iv of companies act 2013 Ppt on our environment for class 10th free download Ppt on earth movements and major landforms in canada Ppt on interview etiquettes of life Ppt on elements and their symbols Ppt on online shopping websites Ppt on bluetooth based smart sensor networks inc Ppt on 3 r's of environment Ppt on duty rosters Ppt on abo blood groupings