1. Interchanges
Module 7

2. Learning Outcomes At the end of this module, you will be able to:
Identify how land uses around freeway interchanges create pedestrian trips
Explain how and why pedestrian crashes occur at interchanges (driver expectation of pedestrians is very low; high-speed, free-flow movements)
Select slow-speed, right-angle urban designs
Pedestrian safety is rarely considered when freeway interchanges are designed; yet many pedestrian crashes occur at the ramp termini, because drivers don’t expect pedestrians when transitioning from high-speed freeway driving to urban arterials.
Designing for Pedestrian Safety – Interchanges

3. Land Use, Vehicles and Pedestrians
Medford OR
Large commercial tracts generate traffic
Employees walk to jobs at retailers, restaurants, service stations, & hotels
Visitors walk to and from restaurants and hotels
Pedestrians must cope with vehicles entering and exiting the freeway
Though freeway interchanges are intended for the transfer of traffic from surface streets to freeways, they often attract large commercial land uses and generate traffic not related to freeway use. This additional traffic makes it even harder for those who must cross the freeway on foot, or those who need to walk to the commercial land uses, such as employees.
Designing for Pedestrian Safety – Interchanges

4. And some non-interchange crossings
Typical city has a few freeway interchanges
Non- interchange crossings are easier for pedestrians
Interchanges have many conflicts
This slide illustrates a common situation in many cities bisected by a freeway: not all cross streets are connected (they’ve been severed by the freeway), limiting travel across the freeway. Some local streets do go over or under the freeway, which is preferable for pedestrians. But pedestrians also need access across the freeway at streets that are freeway interchanges; the challenges there are the freeway ramps as traffic moves on and off the freeway onto and off local streets.
The more non-freeway connections the better.
Designing for Pedestrian Safety – Interchanges

5. Accommodate all pedestrian movements
1. Through interchange (east-west along arterial)
2. Across the arterial (north-south)
Animated, click to bring in animated text and graphics (linked)
In a classic diamond interchange, the four ramp termini are roughly equivalent to the four legs of a standard intersection, except they’re separated be several hundred feet. This means each approach can be designed for pedestrian safety using the design principles learned so far.
Designing for Pedestrian Safety – Interchanges

6. These inside crosswalks may be closed
The inner two crosswalks can be closed, as there should be no pedestrian accessible land uses within the limits of the interchange itself. All other crosswalks should be open: the 4 across the on/off ramps (for pedestrians walking across the freeway along either side of the arterial) and the two across the arterial at each end (for pedestrians wishing to cross the arterial between land uses). Closing any of these crosswalks makes some destinations inaccessible, or forces pedestrians to travel out of direction, increasing their exposure to traffic.
These crosswalks must be open
Designing for Pedestrian Safety – Interchanges

7. Interchange then becomes a Large Intersections
Animation: on click pictures slides together to form large intersection.
Point: Design principles of interchanges similar to those of large intersections

8. This large suburban/commercial interchange still looks like a place pedestrians can use. Each leg of the interchange looks like a standard intersection. Features such as separated sidewalks, islands and crosswalks are used.
Baker City OR
Design interchanges to look like an intersection, then drivers are more likely to expect pedestrians
Designing for Pedestrian Safety – Interchanges

9. Consider each terminus as ½ an urban intersection
Close-up: In a classic diamond interchange, the four ramp termini are roughly equivalent to the four legs of a standard intersection, except they’re separated by several hundred feet. This means each approach can be designed for pedestrian safety using the design principles learned so far.
Consider each terminus as ½ an urban intersection
Designing for Pedestrian Safety – Interchanges

10. Avoid free-flow movements…
Asheville NC
Traffic entering or leaving a freeway under free-flow conditions may not expect to see pedestrians crossing their paths at the ramps.
… they are difficult for pedestrians to cross
Designing for Pedestrian Safety – Interchanges

11. Positive Example: Reconfigured Ramp Terminus
Springfield OR
Old ramp alignment
This photo shows how the alignment was reconfigured so the ramp now comes in at a right angle. The area with low vegetation is where the old ramp used to be.
Flat angle = wide crossing & high-speed turns
Tight angle = short crossing & slow speed turns
Designing for Pedestrian Safety – Interchanges

12. Positive Example: Reconfigured Ramp Terminus
Springfield OR
Crosswalk is a lot shorter too. Notice that they saved a bit of money by aligning the sidewalk to use part of the old bridge. But think about how much money they could have saved in the first place if they hadn’t built the wider, curved bridge in the first place.
Red line = old crosswalk
Green line = new crosswalk
Designing for Pedestrian Safety – Interchanges

13. Where free-flow ramps exist, good crosswalk placement is critical
Reminder from geometry module – crosswalk placement requires balancing goals:
Shortest crosswalk length
Minimal crosswalk setback to:
Reduce out-of-direction travel
Provide good sight lines between peds and motorists
Proper ramp placement
These three goals should be met. Meeting only one of these goals can create dysfunctional crossings, for example if the crosswalk is too far from the intersection, or doesn’t line up with the curb ramps.
Designing for Pedestrian Safety – Interchanges

14. Existing crosswalk is here Crosswalk could be here
Animated slide: Click to show a better location for the crosswalk.
Traffic entering or leaving a freeway under free-flow conditions may not expect to see pedestrians crossing their paths at the ramps. These designs make it difficult to place crosswalks appropriately, but it can be improved in many cases.
Salem OR
Where free-flow ramps are used (least desirable) Crosswalk should be placed where it’s visible
Designing for Pedestrian Safety – Interchanges

15. Barrier should not obscure crosswalk
These barriers hide the crosswalk ahead. The principles of crosswalk placement learned in the previous module apply here too.
Salem OR
Barrier should not obscure crosswalk
Designing for Pedestrian Safety – Interchanges

16. Crosswalk Placement
Choosing the best crosswalk placement where it’s not clear what’s most logical for the driver or the pedestrian:
3 choices:
Most direct route
Shortest crosswalk
“Compromise” - midway solution
The next few slides illustrate the dilemma designers face when trying to determine where to place crosswalks at a non-conventional intersection. Three are three choices: Most direct route, shortest crosswalk, “compromise” - midway solution
Designing for Pedestrian Safety – Interchanges

17. Most Direct Route Designing for Pedestrian Safety – Interchanges
The most direct route simply links the approach sidewalks in a direct line. It is the shortest walk overall, but has problems: it’s the longest crosswalk, and pedestrians can’t see approaching traffic from behind.
Designing for Pedestrian Safety – Interchanges

18. Shortest Crosswalk Designing for Pedestrian Safety – Interchanges
Animated: click to make pedestrian cross and car move.
The shortest crosswalk has an advantage, but it also has problems: it’s the longest walking distance overall, and pedestrians cross where they can’t be seen by approaching traffic.
Designing for Pedestrian Safety – Interchanges

19. Midway Solution – Balances Goals
Animated: click to make pedestrian cross and car move.
The midway solution is halfway between the most direct route and the shortest crosswalk. The overall walk is still fairly short, the crosswalk is not too long, and pedestrians can see approaching traffic and can be seen by drivers.
Designing for Pedestrian Safety – Interchanges

20. Where to place crosswalk?
Shortest crossing
Midway
Most direct route
Where to place crosswalk?
Observe pedestrians
Washington DC
Animated; don’t click, it’s automated.
The elderly gentleman seeks the security of a crosswalk, the younger adult sees the advantage of the straight through path, though she has to look over her shoulder for traffic. A midway point crosswalk would serve both users best.
Note the excessive signing – someone has noticed a problem with the visibility of the crosswalk. Extending the nose of the gore point would help too.
Note the darkness in the underpass. Drivers may not be able to perceive pedestrian in the underpass due to the difference in the level of ambient light in the open and in the underpass.
Younger woman takes direct route (looks over shoulder)
Older man seeks crosswalk
Midway would be used by both
YIELD TO PED signs indicate a problem
Designing for Pedestrian Safety – Interchanges

21. Single Point Urban Interchange (SPUI
SPUI = Single Point Urban Interchange. It’s a new type of interchange increasingly popular in urban areas, at it takes up much less right-of-way.
Designing for Pedestrian Safety – Interchanges

22. Single Point Urban Interchange
Takes less ROW than split diamond
Animated. SPUI’s are characterized by one signal that controls 3 movements:
Through movement on surface street
Opposing left turns from surface street to on-ramps
Opposing left turns from off ramps to surface street.
Through movements
Left turns in one direction
Left turns in other direction
Signal timing; 3 movements are run through one signal
Designing for Pedestrian Safety – Interchanges

23. How to make SPUI work for pedestrians:
Provide continuous sidewalks
Break up crossings into several small steps
Use good geometry; create tight, right-angle crossings;
Make it clear to drivers where to expect pedestrians
The pedestrian faces 4 conflict points when proceeding through a SPUI; each must be treated to ensure pedestrian safety. The rest of the slide is self-explanatory.
Designing for Pedestrian Safety – Interchanges

24. SPUI Pedestrian crossing sequence:5
Ped proceeds on sidewalk on or under bridge 7
Ped proceeds on island 3
Ped proceeds on island 9
Ped continues on his merry way 8
Ped crosses exit lane; stop controlled; drivers yield to peds 6
Ped crosses exit lane; signal controlled 4
Ped crosses entry lane; signal controlled 1
Ped walks next to well defined right-turn lane (RTL) 2
Ped crosses RTL at a point with good visibility; drivers yield to peds
Animated: This slide illustrates how to cycle pedestrians though a Single Point Urban Interchange. Walk through each of the 9 points one at a time. Items number 2 and 8 may need to be signal-controlled depending on the number of lanes to cross and other factors.
Designing for Pedestrian Safety – Interchanges

25. Vehicle phase 1 Vehicle phase 2 Vehicle phase 3
Possible ped crosswalks
With most SPUIs there is never a phase when pedestrians can cross the urban arterial without conflict
Animated.
The first click shows where it might be desirable to put in pedestrian crosswalks if there are land uses near the interchange that attract pedestrians. Then it shows how each of the vehicle phases conflicts with the possible pedestrian crosswalks. Finally, the possible solutions are presented.
Solution 1 provides a two-step crossing that fits in with the two left turn phases (a median is required).
Solution 2 places crosswalks at a nearby signalized intersection, which is fine if there is a signal fairly close (this is the most common solution).
Other possible solution is to provide an exclusive pedestrian phase
Solution 1: Two-step crossing (one step during vehicle phase 2 and the other during vehicle phase 3 NOTE: requires median refuge & Ped Signals
Solution 2: Nearby midblock signalized ped crossing, or nearby signalized intersection with crosswalks
Designing for Pedestrian Safety – Interchanges

26. Getting Pedestrians Across a SPUI
Animated.
The first click shows where it might be desirable to put in pedestrian crosswalks if there are land uses near the interchange that attract pedestrians. Then it shows how each of the vehicle phases conflicts with the possible pedestrian crosswalks. Finally, the possible solutions are presented.
Solution 1 provides a two-step crossing that fits in with the two left turn phases (a median is required).
Solution 2 places crosswalks at a nearby signalized intersection, which is fine if there is a signal fairly close (this is the most common solution).
Other possible solution is to provide an exclusive pedestrian phase
Vehicle phase 1
Designing for Pedestrian Safety – Interchanges

27. Getting Pedestrians Across a SPUI
Animated.
The first click shows where it might be desirable to put in pedestrian crosswalks if there are land uses near the interchange that attract pedestrians. Then it shows how each of the vehicle phases conflicts with the possible pedestrian crosswalks. Finally, the possible solutions are presented.
Solution 1 provides a two-step crossing that fits in with the two left turn phases (a median is required).
Solution 2 places crosswalks at a nearby signalized intersection, which is fine if there is a signal fairly close (this is the most common solution).
Other possible solution is to provide an exclusive pedestrian phase
Vehicle phase 2
Designing for Pedestrian Safety – Interchanges

28. Getting Pedestrians Across a SPUI
Animated.
The first click shows where it might be desirable to put in pedestrian crosswalks if there are land uses near the interchange that attract pedestrians. Then it shows how each of the vehicle phases conflicts with the possible pedestrian crosswalks. Finally, the possible solutions are presented.
Solution 1 provides a two-step crossing that fits in with the two left turn phases (a median is required).
Solution 2 places crosswalks at a nearby signalized intersection, which is fine if there is a signal fairly close (this is the most common solution).
Other possible solution is to provide an exclusive pedestrian phase
Vehicle phase 3
Designing for Pedestrian Safety – Interchanges

29. Alternative Intersections/Interchanges
The next several slides illustrate some new interchange concepts that are being tried in various places around the country; these can typically be made to work for pedestrians
Alternative Intersections/Interchanges
Designing for Pedestrian Safety – Interchanges

30. Four Intersection Concepts
Designing for Pedestrian Safety – Interchanges

31. Two Interchange Concepts
Designing for Pedestrian Safety – Interchanges

32. Double Crossover Diamond
Designing for Pedestrian Safety – Interchanges

33. Designing for Pedestrian Safety – Interchanges

34. Double Crossover Diamond
Kansas City MO
Leading up to the protected Center Crossing
Designing for Pedestrian Safety – Interchanges

35. Double Crossover Diamond Walking down the Protected Center
Kansas City MO
Designing for Pedestrian Safety – Interchanges

36. Double Crossover Diamond
Kansas City MO
Multiple LED Lighting fixtures embedded in the wall
Designing for Pedestrian Safety – Interchanges

37. Displaced Left Turn Interchange
Designing for Pedestrian Safety – Interchanges

38. Let’s Recap Why is controlling land uses important?
Attractors create pedestrian demand
Why do ped crashes occur at freeway interchanges?
Driver expectation of pedestrians is very low
They’re driving fast
What kind of movements should be avoided?
High-speed, free-flow
How can one mitigate for these problems?
With slow-speed, right-angle urban design
With improved crosswalk placement
Many designers don’t consider pedestrian safety when designing freeway interchanges; yet many crashes occur at the ramp termini, because drivers don’t expect pedestrians when transitioning from high-speed freeway driving to urban arterials.
Designing for Pedestrian Safety – Interchanges

39. Learning Outcomes You should now be able to:
Identify how land uses around freeway interchanges create pedestrian trips
Explain how and why pedestrian crashes occur at interchanges (driver expectation of pedestrians is very low; high-speed, free-flow movements)
Select slow-speed, right-angle urban designs
Pedestrian safety is rarely considered when freeway interchanges are designed; yet many pedestrian crashes occur at the ramp termini, because drivers don’t expect pedestrians when transitioning from high-speed freeway driving to urban arterials.
Designing for Pedestrian Safety – Interchanges

40. Questions?
Designing for Pedestrian Safety – Interchanges