Udon Ratthaya Expressway ทางพิเศษอุดรรัถยา
Bang Pa-in–Pak Kret Expressway ทางด่วนสายบางปะอิน–ปากเกร็ด
Route information
Maintained by Bangkok Expressway and Metro
Length	32.0 km (19.9 mi)
Existed	2 December 1998–present
Chaeng Watthana–Chiang Rak
Length	22.0 km (13.7 mi)
North end	Chiang Rak Interchange
South end	Si Rat Expressway, Chaeng Watthana Road
Chiang Rak–Bang Sai
Length	10.0 km (6.2 mi)
North end	Outer Ring Road (West) (Kanchanaphisek Road)
South end	Chiang Rak Interchange
Location
Country	Thailand
Highway system
Highways in Thailand Motorways Asian Highways

The Udon Ratthaya Expressway (Thai: ทางพิเศษอุดรรัถยา), also known as the Bang Pa-in–Pak Kret Expressway (Thai: ทางด่วนสายบางปะอิน–ปากเกร็ด), is an expressway in Thailand, located in Nonthaburi, Pathum Thani and Phra Nakhon Si Ayutthaya provinces. The expressway is a controlled-access toll road.^[1]

Udon Ratthaya Expressway was proposed to handle road traffic for the 13th Asian Games which were held at Thammasat University Rangsit Campus in 1998. It was also aimed at reducing road traffic on Vibhavadi Rangsit and Phahon Yothin roads leading northwards out of Bangkok. The first section between Chaeng Watthana–Chiang Rak was opened on 2 December 1998. It is a continuation of the Si Rat Expressway Section C. The second section between Chiang Rak–Bang Sai was opened on 1 November 1999.

According to an official EXAT annual report, the expressway was used by 25,842,029 cars in the 2022 fiscal year, with an average of 74,688 cars per day.^[2]

Kilometre 0 is counted at Chaeng Watthana Interchange.

Udon Ratthaya Expressway
Location	km	Northbound		Facility		Southbound
		Exit destinations (road)	Toll Plaza (Entry)	English	Thai	Toll Plaza (Entry)	Exit destinations (road)
Nonthaburi	0.0	-	no toll plaza (continued from Si Rat)	Chaeng Watthana Interchange	แยกทางด่วนถนนแจ้งวัฒนะ	no toll plaza (continues to Si Rat)	Lak Si, Pak Kret ( Chaeng Watthana Road)
							Pracha Chuen, Bangkok ( Si Rat Expressway)
	2.57	Muang Thong Thani, Sukhothai Thammathirat University (Popular Road)	Muang Thong Thani (Outbound)	Muang Thong Thani Interchange	แยกทางด่วนเมืองทองธานี	Muang Thong Thani (Inbound)	Muang Thong Thani (Popular Road)
	5.18	Tiwanon Road, Nonthaburi Bridge ( Si Saman Road)	Si Saman (Outbound)	Si Saman Interchange	แยกทางด่วนศรีสมาน	Si Saman (Inbound)	Don Mueang ( Si Saman Road)
Pathum Thani	12.70	Ban Klang Intersection, Pathum Thani ( Rangsit–Pathum Thani Road)	Bang Phun (Outbound)	Bang Phun Interchange	แยกทางด่วนบางพูน	Bang Phun (Inbound)	Rangsit ( Rangsit–Pathum Thani Road)
	20.02	Chiang Rak, Thammasat University Rangsit ( Chiang Rak Road)	Chiang Rak (Outbound)	Chiang Rak Interchange	แยกทางด่วนเชียงราก	Chiang Rak (Inbound)	Chiang Rak, Thammasat University Rangsit ( Chiang Rak Road)
Phra Nakhon Si Ayutthaya	29.40	Bang Sai, Bang Bua Thong ( AH2 Kanchanaphisek)	Bang Pa-in (Outbound) - exit only	Kanchanaphisek Ring Road Interchange	แยกวงแหวนกาญจนาภิเษก	Bang Pa-in (Inbound)	Bang Pa-in, Ayutthaya, Wang Noi ( AH2

• Controlled-access highways in Thailand
• Expressway Authority of Thailand