Vehicle Discharge Lamp, Vehicle Discharge Lamp Device, Lighting Circuit Combined Type Vehicle Discharge Lamp Device, and Lighting Circuit

A vehicle discharge lamp substantially not using mercury, comprising:

• a light emitting part in which a discharge space is defined and into which a discharge medium including metal halide and rare gas are sealed;
• and
• a pair of electrodes arranged in the discharge space,
• wherein a spherical length b, which is a length in a tube axial direction of the light emitting part, is 7.5 mm to 8.5 mm and a thickness volume V of the light emitting part is 50 mm3 to 100 mm3, and wherein the following formula is satisfied:
• −20≦(a−35)×5.5+(x−13.5)×10+(1.85−t)×100+(2.5−d)×100≦20
• wherein
• a:
• power [W] supplied in a stable lighting time, satisfying:
• 22<a≦26
• x:
• pressure [atm] of rare gas sealed in the discharge space and ranging 10˜17 atm
• t:
• thickness [mm] of a part where a wall thickness of the light emitting part is maximum and ranging 1.3˜1.85 mm
• d:
• inner diameter [mm] of a part where the wall thickness of the light emitting part is maximum.