Why Are There Two Sides of Roads in the United States?

When discussing the design of roads in the United States, it's common to notice the 'two sides' on divided highways. Why are these roads designed this way? How does this design contribute to safer driving and better urban planning?

The Purpose of Divided Highways

Divided highways, also known as dual-carriageways, are a design feature where the road is split into two separate lanes of travel, separated by a median. This split is not always necessary everywhere, but where room permits, it offers several advantages.

1. Reducing Head-On Collisions
One of the primary reasons for dividing roads is safety. Cars on one side can’t easily cross the center line and hit oncoming traffic. This reduces the risk of head-on collisions, which are often fatal.

2. Improved Traffic Flow
Divided highways also minimize the risk of traffic blockages. If an accident occurs on one side of the road, the other lane can still allow traffic to pass, maintaining the flow of transportation.

3. Safer U-Turns
Occasional turn-arounds in the center median strip can help drivers make safer U-turns. This is particularly useful in rural areas where the median may be lined with trees or walls for further safety.

The Limitations of Divided Highway Design

While the benefits of divided highways are clear, their implementation comes with limitations. The condition 'where room permits' is often the crux of the issue.

1. Urban Areas and Space Constraints
In cities, space is often a limiting factor. Existing buildings and infrastructure make it difficult to create enough space for a divided road. Massive demolition of buildings would likely be required to make room for this type of design.

2. Historical Development
Some older cities were not built with divided roadways in mind. Therefore, the infrastructure around these roads makes it challenging to re-engineer the roads to accommodate this design. In these cases, urban planners may opt for other solutions, such as one-way traffic patterns, to achieve similar traffic flow benefits.

3. Rural vs. Urban Planning
In rural areas, more space is often available, making it easier to implement divided highways. Rural roads may repurpose some farmland on either side to accommodate the design.

The Cost and Design of Roads

The decision to build a road with divided lanes is not made arbitrarily. There are considerations such as safety, traffic flow, and cost.

1. Cost Reduction Through Two-Way Traffic
Most roads are designed to allow two-way traffic, which makes the construction process more cost-effective. This design ensures that the road can be utilized in both directions, reducing the need for separate lanes in opposite directions.

2. Historical Traffic Patterns
Many roads in older cities are built with one-way traffic in mind. This is often due to safety concerns and the cost-related issues of repurposing existing infrastructure. However, as cities grow and traffic patterns change, some may be repurposed to accommodate two-way traffic to better utilize the space and reduce congestion.

3. Safety Considerations in Urban Development
Traffic patterns in urban areas often focus on minimizing conflicts between vehicular and pedestrian traffic. One-way streets and pedestrian walkways help in creating safe and manageable spaces for both vehicles and pedestrians.

Conclusion

Divided highways, or dual-carriageways, are an important aspect of road design in the United States. They offer significant safety benefits and can improve traffic flow. However, they come with challenges of space availability and historical infrastructure. Understanding the reasons behind their design and the limitations helps in making informed decisions for urban and rural planning.

Keywords: divided highway, divided road, road design