public class JVFCard : IXmlSerializable
{
    public string driver_name;
    public string report_date;
    public string pm_code;
    public string job_number;
    public string trip_necessary;
    public string[] travel_q;

    public System.Xml.Schema.XmlSchema GetSchema()
    {
        throw new NotImplementedException();
    }

    public void ReadXml(XmlReader reader)
    {
        throw new NotImplementedException();
    }

    public void WriteXml(XmlWriter writer)
    {
        writer.WriteElementString("driver_name", driver_name);
        writer.WriteElementString("report_date", report_date);
        writer.WriteElementString("pm_code", pm_code);
        writer.WriteElementString("job_number", job_number);

        writer.WriteStartElement("travel_q");
        for (int i = 0; i < travel_q.Length; ++i)
        {
            writer.WriteStartElement("string");
            writer.WriteAttributeString("id", (i + 1).ToString());
            writer.WriteValue(travel_q[0]);
            writer.WriteEndElement();
        }
        writer.WriteEndElement();
    }
}

public class JVFCard
{
    public string driver_name;
    public string report_date;
    public string pm_code;
    public string job_number;
    public string trip_necessary;

    [XmlArrayItem("string")]
    public Travel[] travel_q;
}

public class Travel
{
    [XmlAttribute]
    public int Id;

    [XmlText]
    public string Value;
}

var jvfcard = new JVFCard
{
    driver_name = "",
    report_date = "06/16/2015",
    pm_code = "",
    job_number = "",
    trip_necessary = "",

    travel_q = new Travel[5] {
        new Travel { Id=1, Value="wer" },
        new Travel { Id=2, Value="wer" },
        new Travel { Id=3, Value="wer" },
        new Travel { Id=4, Value="wer" },
        new Travel { Id=5, Value="wer" } }
};