The following highways are numbered 340:

• Manitoba Provincial Road 340
• New Brunswick Route 340
• Newfoundland and Labrador Route 340
• Nova Scotia Route 340
• Prince Edward Island Route 340
• Quebec Route 340
• Saskatchewan Highway 340

• National Highway 340 (India)

• Japan National Route 340

• Fv340

• U.S. Route 340
• Arkansas Highway 340
• Colorado State Highway 340
• Georgia State Route 340 (former)
• Hawaii Route 340
• Indiana State Road 340
• Missouri Route 340
• Nevada State Route 340
• New York State Route 340
• Ohio State Route 340
• Pennsylvania Route 340
• Texas:
  • Texas State Highway 340 (former)
  • Texas State Highway Loop 340
• Wyoming Highway 340