Bridges and culverts can be great indicators of when a highway was built and by whom it was built. In California, there are a few different styles of railing which can be used to put a relative date on a particular bridge when they don’t have date stamps on them. Other indicators may be used when the bridge rail has been modified or even replaced by modern rail. Styling elements on the superstructure vary depending on age. Older bridges tend to be more ornate than more modern structures. This page will serve as a guide to these styles and help to increase understanding of what goes into the design of these bridges.
Over the past week or so, I’ve been working to add more content to the site. Not to avoid completing the existing pages either, just to fill in some gaps. Here are some of the updates:
New Website Feature – a new Discussion Forums feature has been added. It is an experiment, so we’ll see where it goes.
New Section – Civic Information – These pages give links to every incorporated city in Southern California and give a bit of information about each county as well. The links are finished, but the format is still being worked on.
New Page – Seeking Old Highways – A while back I was working on putting up a guide to looking for old roads, bridges, and signs. It is still a work-in-progress, but has now been more given its own page in the Highways section.
Additional Historic Photos – Old photos of US 101 in the Los Angeles area have been added to the US 101 page.
Concrete is a very durable material. It has many uses, though for our purposes – roadway surfaces, curbs, and sidewalks. Local roadways, such as concrete city streets, won’t be covered in this post. Bridges will be covered in a later post. This durability allows us to get either a relative date of when a roadway was paved or built to an absolute date when we find a date stamp.
Style of Paving
As technology has evolved, so has concrete paving. The first concrete paving along State Highways was 10-12′ wide, usually not reinforced with steel. These roads were paved in one single slab of concrete. Roadways of this style were paved from around 1910 to 1915. After 1915, wider paving was used and was generally reinforced. Wider paving ran from 15′, 18′, and a “full” 20′. These are usually referred to as “Single Slab Paving”.
Sometime around 1923, longitudinal joints were added to the concrete paving. This created a “Twin Slab” roadway. This style persists today, though greatly changed. Early Twin Slab roadways had fewer expansion joints running across the lane. After around 1926, this problem was worked out by adding more frequent joints. By this time, each lane was a “standard” 10′. This standard remained until the late 1940’s when lane width started to widen to 12′.
Contractors, either by requirement or pride, usually stamp the concrete roadway, curb, or sidewalk with a date stamp. These stamps vary in location, size, and information. Date stamps marked either the beginning or end of a days paving. As such, the stamp tended to be located near an expansion joint. A general rule with date stamps is “find one, you can find the rest”. This is mostly about the location. Some stamps are in the middle of a lane, some are to the side of a lane. The orientation also varies with stamps. The information contained in these stamps also varies. Early stamps just have the contractor and the date. Later stamps added the engineering station. Without going into too much detail, at this time, about engineering stations, the “zero” point is at the beginning of a road section or project. With little exception, I have had little success in finding a date stamp on Single Slab roadways. Twin Slab roadways are much better with stamps.
Using date stamps and styles as a guide, you can easily date a roadways construction to within a few years. There are other methods you can use, but these aren’t covered here. Some will be covered in later posts. Stay tuned for more posts. Bridges, Road Signs, and more will be covered in the future. If you have any questions, please post a comment or send me a message.