Interchanges

Highway interchanges allow traffic to move from one roadway to another while maintaining speed. They accomplish this by separating traffic from grade and re-inserting into another stream while not directly crossing that stream.

Here are some different types of interchanges.

Full Diamond Interchange

Directional Interchange

Single Point Interchange

Two-Level Cloverstack Interchange

Y-Interchange

Half-Clover Interchange

Trumpet Interchange

Diverging Windmill Interchange

Windmill Interchange

Turbine Interchange

Roundabout Interchange

And there are many more...

Pedestrian Walkways

This post will feature different components of sidewalks and some other pedestrian walkways.

Very Old Sidewalks

Sidewalks have been around for a very long time. Pictured above are sidewalks beside a street in Pompeii, Italy.

Japanese Crosswalk Intersection

When sidewalks cross streets, they are called crosswalks. Some crosswalks cross intersections diagonally.

Pathway

When a sidewalk leaves the roadway, it can be referred to as a pathway.

A Square Curb

Curbs are the edge of a sidewalk. They can be made in a variety of profiles.

A Slanted Curb

A Soft Curb

Sidewalk with Verde Strip

Sidewalks can be separated from the street by a strip of planting.

Sidewalk with Bike Path

Sidewalks can include a bike path.

Sidewalk Ramp

 Sidewalks need to be accessible to wheel chairs or other wheeled devices such as baby strollers.

Side Walk leading to a Ramp leading to a Cross Walk

Sidewalk Art

Sidewalk art can be amazing! CLICK ON THE IMAGE for a close-up.

Four-Way Stop

Four-way stops, also known as all-way stops, are a very common road way feature.

A Typical Four-Way Stop

Here are some common elements of these traffic control devices.

Typical Four-Way Stop Sign

4-way intersections are always marked as such, and you are always required to come to a complete stop.

'STOP' painted on the road way

Lettering will frequently be applied to the area directly in front of the intersection to further indicate to the driver that a complete stop is required.

Blinking Lights

Blinking lights will sometimes be used to further draw attention to the driver that they must come to a complete stop.

Typical Layout of a 4-Way Stop

A 4-way stop will typically have the above geometry.

A Crosswalk

4-way stops will sometimes incorporate a cross-walk.

Cross walk sign

Additional cross walk signage is sometimes used.

Cross walk signal

Pedestrians will sometimes be signaled to cross with a cross walk signal at busier intersections.

Multi-Lane 4-way Stop

A four-way stop may have more than two lanes coming from each direction.

Crowded Intersection

Sometimes a simple 4-way stop is not sufficient to handle traffic volumes.

NEXT TIME: PEDESTRIAN WALKWAYS

Bridges

Here are some examples of bridges with an emphasis on older, more primitive stone arch bridges. Particularly interesting is the Bamboo bridge from Indonesia.

Ancient Stone Arch Bridge, Greece

Primitive Suspension Bridge

Collapsed Section Repaired with Temporary Bridge

Bamboo Bridge, Indonesia

Ancient Stone Bridge,Yemen

Ancient Arch Bridge, Iran

Suspension Bridge, Japan

Raised Bridges, Chicago

Cable Stay Bridge, France

Foot Bridge, France

Rail Crossings

Rail crossings, formally referred to as "level crossings," are a common type of traffic control feature. This is where two modes of transportation intersect with one of them being a train rail line and, most typically, a street.

Typical arrangement of modern level crossing safety system

Level crossings were originally manned by a man in a booth who, upon the approach of a train, would either wave a flag to warn of the approach or clear livestock from the tracks. The first mechanical warning gate systems were more concerned with clearing and securing the track from livestock and so would incorporate an actual gate to physically prevent animals from occupying the tracks.

Example of older-style level crossing

As the automobile came to dominate the roadways, the mechanical warning system became focused on drawing attention to the motorist of approaching train traffic and relying on the discretion of the driver to not occupy the track area.

Signal styles vary from county to country as to levels of traffic impediment, from a simple manually operated gate to much more complex systems.

Warning Cross

Manually Operated Gate

Protected Pedestrian Level Crossing

Belgian crossing sign

A 'Wig-Wag' Type Signal

Gate with Guard

Raised Panel Gate

Do Not Try to Cross In Front Of a Train

NEXT WEEK: Bridges