Motorists could legally drive 70 miles per hour on a stretch of Interstate 93 north of Concord, N.H., under a bill headed to the state Senate. The New Hampshire House voted 292 to 65 Wednesday to raise the limit from 65 miles per hour from Exit 18 to the Vermont border. The current limit would remain through Franconia Notch. The House rejected bills raising the limit as high as 75.