Hierarchies and Intersections Flashcards
What 2 factors must a transport system juggle?
Access and movement.
What types of roads have high access?
Local streets
What types of roads have high movement?
Freeways, expressways.
Which roads balance between both access and movement?
Major arterials.
If movement was on the y axis and access on the x, which letter does the curve represent?
It looks like the middle section of an ‘s’
What are the key principles of self-explaining roads?
1) Functionality
2) Homogeneity
3) Predictability
4) Forgivingness
5) State awareness
What are self-explaining roads?
Roads that make it clear to drivers what road type they are on. They can then adjust their driving accordingly.
What are the key defining attributes for street patterns?
- Rectilinear or curvilinear road links
- Grid-like, tree-like (tributary) or radial link patterns
- T or X intersections
- Small cells connected to other cells.
What pattern is being pushed currently?
Grid networks called “New Urbanism”
Two factors that will influence the road network?
Speed and volumes
Will curvilinear designs have slower or faster speeds?
Slower speeds
Will networks with shorter links and more intersections have slower or faster speeds?
Slower speeds
What will tributary networks do to the traffic volumes?
Limit through traffic along minor streets, but funnel higher volumes onto the top-level streets.
What are factors network connectivity should be designed to?
- Shorter travel distances
- Increased number of alternate routes
- Increased opportunity or interactions
- Improved access to public transport, walking and cycling networks
- Good access to final destinations
What two key elements are networks comprised of?
Nodes - road/rail intersections/endpoints or terminals/stations etc where transport stops
Links - actual roads/rails
What are the two types of link connections?
- Series
- Parallel
What are the 7 basic topologies? (the combination of nodes and links in different ways)
- Ring
- Star
- Mesh
- Fully connected
- Line
- Tree
- Bus
What are the 5 main types of intersections?
1) Uncontrolled - minor roads
2) Priority - major roads, giveway/stop on minor roads
3) Rotary - roundabout priority
4) Signalised - major conflicted flows are separated in time
5) Grade separated - separation in space of major conflicting flows by overbridges and underpasses
What factors are considered when selecting intersection?
1) Efficiency - delays, stops, fuel
2) Safety
3) Other factors - effect of adjacent land, road hierarchy
What are the 10 principles of intersection design? pg 69 lol
1) Adequate capacity and approx form of control
2) Reduced conflict points
3) Minimise area of conflict
4) Separate conflict points
5) Give preference to major flows
6) Control veh speed
7) Clearly define veh path
8) Provide adequate sight distance (but not too much)
9) Clear form of control for approaching road users
10) Provide for all road users
What is channelisation?
Secondary roads to separate different flows of traffic from the main traffic flow.
What are the disadvantages of channelisation?
1) Introduction of an obstruction on the road
2) Restriction of parking/access to property
3) Increased drainage and pavement maintenance problems
Classification of roundabouts.
1) Conventional - raised central island, approaches not flared
2) Small - raised central island, approaches flared
3) Mini - flush (small rise), approaches flared.
How should roundabouts be designed?
- Adequate entry width
- Adequate circulation space
- Sufficient central island diameter
- Deflection of traffic to the left on entry, promoting rot movement
- Simple layout
How are veh speeds controlled at roundabouts?
Kept low with adequate deflection of crossing movement.
- Max safe of 50km/h
- Max safe of 30km/h with bikes and peds
