What is the difference between diversion and increasing the number of lanes?
4 Answers
Diversion and increasing the number of lanes differ in meaning, arrangement, and purpose. Different meanings: A diversion lane is an auxiliary lane designed for vehicles to complete the diversion process. The basic number of lanes refers to the required number of lanes on a road or a specific section, determined based on traffic volume and capacity requirements. Different arrangements: Diversion points are typically located at the entrance of a level intersection or the exit of a highway (elevated road) ramp. Increasing the number of lanes is applied to wide roads with good traffic conditions and high vehicle flow. Different purposes: Diversion points are measures taken to ensure orderly traffic flow, enhance safety, smoothness, and improve traffic capacity. Increasing the number of lanes aims to achieve balance at the points where the main road merges with or diverges from ramps. A diversion sign is an indication sign, signaling the presence of a diversion lane ahead, and vehicles should proceed straight or exit the main lane as directed by the arrows. Diversion is a traffic engineering term describing the phenomenon where a single traffic flow splits into two or multiple flows.
I previously studied traffic planning and found that these two serve completely different purposes. Diverting traffic involves creating new branch roads on existing routes to guide vehicle flow, such as highway exit ramps which are classic diversion designs that redirect vehicles in specific directions. Increasing the number of lanes, on the other hand, is purely about widening the road and adding more lanes. The actual construction differences are significant: diversion requires complete new route projects, which are costly and involve land acquisition, while adding lanes mainly focuses on road widening. From observing elevated road renovation projects, I've noticed that diversion is more suitable for optimizing traffic networks, whereas increasing lanes directly enhances the capacity of a single road section. When dealing with complex intersections, engineers often achieve the best results by combining both approaches.
Last time I drove through a construction zone, I really felt the difference between the two. Diversion is like putting up a new sign at a congested intersection to guide you onto a side road, requiring you to change lanes in advance, and you can often see the triangular split island. Adding lanes is more straightforward—suddenly, three lanes become four, allowing you to drive through without changing your route. The most noticeable feeling is that with more lanes, traffic disperses, and the number of times you need to brake decreases. On the other hand, at diversion points, you always have to be careful not to miss the exit. During rush hour, adding lanes does a better job of easing congestion. Construction crews also prefer widening lanes because the construction period is shorter and the impact is smaller.
In our traffic design studies, the professor always emphasized the different core objectives. Traffic diversion focuses on optimizing route choices for vehicles to prevent congestion on a single road, commonly seen in interchange hubs. Lane addition simply increases the throughput per unit time, mainly implemented on straight road sections. One set of calculation data was particularly illustrative: adding two lanes to a four-lane bidirectional road could increase traffic flow by 40%; whereas diverting 30% of vehicles could raise the main road's speed by 15 km/h. The construction differences are even more pronounced—lane widening barely touches the foundation, while diversion involves relocating the entire pipeline network.
