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

Roundabouts

In this first post we'll consider the modern roundabout and it's various components.

Modern Roundabout

Roundabouts differ from the a traffic circle, pictured below, in several distinct ways.

Traffic Circle

A roundabout always has some sort of signage which indicates to traffic entering the roundabout to yield to traffic already in the system.

Yielding Signage Placement

A traffic circle may not have this function, and will have a variety of rules or driving procedures governing how traffic navigates the system.

A roundabout will always slow traffic, while at the same time eliminating some of the disadvantages of a traditional intersection.

Sidewalks for pedestrians or bicyclists are typically offset from the circular traffic path for safety as can be see clearly from this photo.

Crosswalk Placement

To increase pedestrian safety, pedestrian islands or refuge islands are often incorporated.

Refuge Island

Roundabouts will typically have a center island which serves the function of a visual barrier for drivers entering the system so that they focus on traffic moving toward them and ignore traffic entering from the opposite side or traffic ahead of them thus reducing confusion.

Landscaped Center Island

Traffic flow in roundabouts is always directed only either in the clock-wise or counter-clockwise direction and is indicated with signage.

Traffic Flow Signage

Lighting for roundabouts follows a best practices methodology. It is advised that lighting be focused on the center island so that a driver encountering a roundabout is not surprised by it's presence in the roadway.

Roundabout Lighting

Roundabouts will also incorporate bicycle lanes.

Bicycle Lane Placement

Or pedestrian underpasses to increase safety.

Pedestrian Underpass under a Roundabout

NEXT WEEK: Railroad Crossings