4.1 Intersection Priority & Right-of-Way
Key Takeaways
Under section 71(2) of the Land Traffic Act, when two vehicles reach an uncontrolled junction of equal roads at the same time, the driver must give way to the vehicle on the left.
A vehicle already inside the junction goes first (section 71(1)), and on a green light a driver must still wait behind the stop line if the junction is blocked (section 71(3)).
Section 72 identifies the major road by a major-road sign, by stop or give-way controls on the other road, by the larger number of lanes, or by a road meeting a soi.
A driver turning right inside a junction must let oncoming vehicles pass first (section 51(2)), and a driver leaving a private driveway must stop and give way (section 74).
4.1 Intersection Priority & Right-of-Way
Quick Summary: Intersections represent the highest-risk conflict zones on Thai roadways. Under Thailand's Land Traffic Act B.E. 2522 (1979), right-of-way is governed by strict statutory hierarchies. At uncontrolled intersections where roadways are of equal status, a vehicle arriving from the left has priority when both arrive simultaneously. However, major roads (ทางเอก) always hold absolute right-of-way over minor roads (ทางโท). Straight-moving vehicles possess priority over turning vehicles, and drivers executing right turns across oncoming traffic must yield to through traffic and left-turning vehicles.
Navigating road junctions safely requires an exact understanding of legal priority under the Land Traffic Act B.E. 2522 (1979). In Thailand, where traffic flows on the left-hand side of the road, intersection collisions constitute a substantial proportion of severe urban and rural traffic incidents. The Department of Land Transport (DLT) theory examination tests these priority rules rigorously. Candidates must understand not only who holds the legal right-of-way, but also the physical and regulatory cues that define road status and determine mandatory driver duties.
1. Uncontrolled Intersections of Equal Status (ทางแยกที่ไม่มีสัญญาณหรือป้ายจราจร)
An uncontrolled intersection is a roadway crossing devoid of active electronic traffic lights, regulatory priority signs (such as Stop or Yield signs), traffic police direction, or painted transverse stop markings. When traversing an uncontrolled intersection where both crossing roadways are of equal classification and physical width, right-of-way is determined by statutory sequence.
The First-in-Junction Rule (สิทธิของผู้ที่ถึงทางแยกก่อน)
Under Section 71 (1) of the Land Traffic Act, if one vehicle has already entered the intersection boundary before other approaching vehicles reach the junction line, that vehicle has the legal right to clear the intersection first. Approaching drivers must decelerate and allow the vehicle already committed within the junction box to complete its transit safely.
The Simultaneous Arrival Priority: Yield to the Left (Section 71(2))
A classic DLT test question is what happens when two vehicles reach an uncontrolled junction of equal roads at the same time. Section 71(2) says:
- If you arrive at the same time and no vehicle is already in the junction, give way to the vehicle on your LEFT (ให้รถที่อยู่ทางด้านซ้ายของตนผ่านไปก่อน).
- The driver whose vehicle is on the right must wait until the vehicle on their left has crossed.
- This rule is easy to reverse by mistake if you learned to drive in a country that gives priority to the right. In Thailand it is the vehicle on the left.
Uncontrolled T-Junctions (ทางแยกตัวที)
At a T-junction, the continuing road is usually the major road because it has more lanes, or the side road is a soi or has a stop or give-way line (section 72). In that case, traffic on the side road gives way to all traffic on the continuing road. Only if the roads are truly equal does the yield-to-the-left rule apply.
2. Major Road vs. Minor Road Priority (ทางเอก ตัดกับ ทางโท)
Most junctions are not between equal roads. The second half of section 71(2) says that where a major road (ทางเอก) crosses a minor road (ทางโท), drivers on the major road go first.
Drivers coming from the minor road must slow down, stop if necessary, and give way to all traffic on the major road, whether it comes from the left or the right.
How Section 72 Identifies the Major Road
Section 72 of the Land Traffic Act gives these tests, in order:
- A Major-Road Sign: A road marked by a sign as a major road.
- Stop or Give-Way Controls: If your road has a Stop sign (ป้ายหยุด), a Give Way sign (ป้ายให้ทาง), the word หยุด, a solid white stop line (เส้นหยุด), or a broken white give-way line (เส้นให้ทาง), then the road ahead of you is the major road.
- More Lanes: If there are no signs or markings, the road with more traffic lanes is the major road.
- Road vs. Soi or Alley: Where a road meets a soi (ซอย) or alley (ตรอก), the road is the major road.
Section 74 adds a related rule: a driver coming out of a private road or a building's driveway must stop and let traffic on the road pass before entering.
3. Straight-Moving Traffic vs. Turning Vehicles
When multiple vehicles approach an intersection simultaneously from different directions, maneuver priorities dictate legal movement:
Through-Traffic Priority
Vehicles traveling straight ahead hold right-of-way over all vehicles preparing to execute turns. A driver intending to turn left or right must wait until straight-moving cross-traffic and oncoming through-traffic have cleared the intersection.
Right-Turning Maneuvers Across Oncoming Traffic
In Thailand's left-hand drive environment, making a right turn requires crossing directly over the oncoming traffic lane. Consequently, turning right is classified as an inferior-priority maneuver:
- A vehicle intending to turn right must yield to all oncoming vehicles that are traveling straight ahead.
- Section 51(2) says a driver turning right inside a junction must let oncoming vehicles pass first, and turn only when it is safe.
- A right-turning vehicle should also give way to oncoming vehicles turning left into the same road.
- The right-turning driver must halt before reaching the center point of the intersection, keep their steering wheels oriented straight forward, and execute the turn only when an adequate gap in opposing traffic exists.
4. Statutory Priority Summary Reference
| Traffic Conflict Scenario | Priority Holder (Right-of-Way) | Yielding Party | Governing Statutory Rule |
|---|---|---|---|
| Uncontrolled Equal Intersection (Simultaneous Arrival) | Vehicle approaching from the LEFT | Vehicle approaching from the RIGHT | Section 71(2) Land Traffic Act B.E. 2522 |
| Uncontrolled Equal Intersection (Sequential Arrival) | Vehicle that entered the junction first | Vehicles arriving subsequently | Section 71 (1) First-in-junction rule |
| Major Road (ทางเอก) vs. Minor Road (ทางโท) | All vehicles traveling on the major road | Vehicles approaching from the minor road | Sections 71(2) and 72 |
| Oncoming Straight vs. Right Turn | Vehicle traveling straight ahead | Vehicle turning right across it | Section 51(2) |
| Opposing Right-Turn vs. Opposing Left-Turn | Vehicle executing the left turn | Vehicle executing the right turn | Right-turning vehicle cuts opposing lane |
| Road vs. Soi, or Road vs. Private Driveway | Traffic on the road | Vehicle coming out of the soi or driveway | Sections 72(4) and 74 |
5. Defensive Intersection Management & Hazard Perception
Possessing legal right-of-way does not relieve a motorist of the fundamental legal duty to prevent collisions. Under Thai law, drivers approaching intersections must practice defensive driving techniques:
- Deceleration on Approach: Drivers must ease off the accelerator and cover the brake pedal when approaching any junction, regardless of whether they are on a major road.
- Sightline Obstructions: Urban intersections in Thailand frequently suffer from visual obstructions, including high boundary walls, parked delivery vehicles, street vendors, and overgrown vegetation. Motorists must adjust approach speed to ensure they can stop within their clear sight distance.
- Motorcycle Filter Awareness: Motorcyclists frequently filter along the left and right flanks of queued traffic. Drivers executing turns must perform physical blind-spot head checks over both shoulders in addition to checking mirrors.
Two passenger cars approach an uncontrolled intersection of equal width and status at the exact same moment. Neither road has traffic signs, signals, or painted stop markings. According to Section 71 of the Land Traffic Act, which vehicle has the legal right-of-way?
The vehicle approaching from the left side has right-of-way
The vehicle approaching from the right side has right-of-way
The larger or heavier vehicle has right-of-way
The vehicle traveling at higher speed has right-of-way
When approaching an intersection without traffic lights, which pavement marking or physical characteristic legally designates your street as a minor road (ทางโท)?
A yellow broken centerline painted down the center of your roadway
A solid white transverse stop line painted across your driving lane
Having a greater road width than the crossing street
Having an asphalt surface while the crossing street is made of dirt
Driver X intends to make a right turn at an intersection, while oncoming Driver Y is traveling straight ahead. Both have a green circular traffic signal. What is Driver X's legal duty?
Driver X has priority because right turns clear the intersection faster
Driver X should honk the horn and accelerate rapidly ahead of Driver Y
Driver X must yield right-of-way to Driver Y and wait until oncoming straight traffic has cleared
Driver X and Driver Y must both stop in the center of the junction and alternate passing
Sections you finish are checked off in the contents.